Integrated polishing film forming processing method and device for liquid metal bearing

Abstract

The application relates to a liquid metal bearing integrated polishing film forming processing method and device, and the liquid metal bearing comprises a mandrel, a bearing bush sleeved outside the mandrel and capable of rotating around the mandrel, a working gap arranged between the mandrel and the bearing bush, and a flow guide groove arranged on the outer surface of the mandrel; the method comprises the following steps: introducing a liquid metal working medium containing nano abrasive grains into the working gap; rotating the bearing bush relative to the mandrel under a first temperature environment, so that the liquid metal working medium forms a liquid metal polishing film in the working gap; polishing and shaping the outer surface of the mandrel and the edge of the flow guide groove by combining the liquid metal polishing film and the nano abrasive grains; introducing a liquid metal working medium without abrasive grains into the working gap to clean the inside of the bearing; and making the liquid metal working medium and the outer surface of the mandrel generate an in-situ interface reaction under a second temperature environment to form a functional film layer. The application reduces heterogeneous pollution, improves the surface precision of the bearing, the edge quality of the flow guide groove and the preparation efficiency of the functional film layer.

Description

Technical Field

[0001] This invention belongs to the field of polishing technology, and particularly relates to an integrated polishing film formation method and apparatus for liquid metal bearings. Background Technology

[0002] High-temperature liquid metal bearings, with their excellent high-temperature resistance, thermal conductivity, and fluid lubrication characteristics, are core components in extreme-condition equipment such as high-end medical CT X-ray tubes, aerospace power units, and nuclear fusion experimental devices. Compared to traditional ball bearings, liquid metal bearings use liquid metal as the lubricating medium, offering significant advantages such as low friction coefficient, strong heat dissipation, low operating vibration, and long service life. They can adapt to harsh working environments with high temperatures, high vacuum, high speeds, and high loads, and have become a key research and application area in the field of high-precision rotating equipment bearings. The guide groove structure, a commonly used hydrodynamic groove type in liquid metal bearings, can enhance the medium's load-bearing capacity and improve the stability of the lubricating film through the hydrodynamic effect. This plays a crucial role in improving bearing lubrication performance and reducing operational wear, and is therefore widely used in the design of various high-precision liquid metal sliding bearings.

[0003] The surface machining accuracy of the bearing working surface, the forming quality of the guide groove edges, and the performance of the interfacial functional film directly determine the friction and lubrication characteristics, sealing performance, and service life of the liquid metal bearing. These are core elements ensuring stable operation of the bearing under extreme conditions. Currently, the processing and manufacturing process of high-temperature liquid metal bearings is relatively fragmented. The industry generally adopts a step-by-step processing technology, sequentially completing processes such as bearing substrate polishing, guide groove mechanical shaping, and surface film formation. In conventional processing, polishing, shaping, and film formation processes require different processing media and specialized processing equipment, resulting in a cumbersome process with poor process integration and a long processing cycle.

[0004] Existing processing techniques suffer from several unavoidable technical defects: First, when changing to specialized media in different processes, media residue is easily generated, introducing foreign contaminants such as solid abrasive particles and impurities. These contaminants adhere to the bearing working surface and the interior of the guide groove, increasing friction and wear during bearing operation and damaging the cleanliness of the lubrication interface, severely affecting the formation stability of the liquid metal lubricating film. Second, traditional polishing processes often use abrasive polishing fluids, which easily cause scratches, pits, and other processing defects on the bearing surface, making it difficult to achieve the surface finishing precision required for high-end bearings. The edges of the guide grooves processed by mechanical milling and etching have problems such as burrs, chipping, and contour distortion. Insufficient groove precision will directly weaken the hydrodynamic effect and reduce the bearing load capacity. Third, the current preparation of surface functional films mostly adopts independent coating processes, which result in low bonding strength between the film and the substrate, poor coating uniformity, and high energy consumption and low preparation efficiency due to independent process settings. Fourth, the multi-media and multi-process processing mode has poor adaptability and high processing cost, making it difficult to meet the needs of high-temperature liquid metal bearings for precise, clean, and integrated mass production.

[0005] Therefore, how to provide an integrated polishing and film-forming process and apparatus for liquid metal bearings that improves preparation efficiency and reduces heterogeneous contamination is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To solve at least one of the above-mentioned technical problems, the present invention provides an integrated polishing and film-forming method for a liquid metal bearing, wherein the liquid metal bearing includes a mandrel, a bearing bush sleeved on the outside of the mandrel and rotatable around the mandrel, a working gap disposed between the mandrel and the bearing bush, and a guide groove disposed on the outer surface of the mandrel; the method includes: S1: Introduce a liquid metal working medium containing a preset concentration of nano-abrasive particles into the working gap; S2: Under the first temperature environment, the bearing bush is rotated relative to the spindle at a first speed, so that the liquid metal working medium forms a liquid metal polishing film in the working gap; S3: Increased temperature and speed, allowing the liquid metal polishing film to work with nano-abrasives to polish and shape the outer surface of the mandrel and the edge of the guide groove; S4: Stop the bearing bush from rotating and introduce non-abrasive liquid metal working medium into the working gap to clean the inside of the bearing; S5: Under the second temperature environment, the bearing is rotated relative to the spindle at the second speed, so that the liquid metal working medium and the outer surface of the spindle undergo an in-situ interface reaction to form a functional film layer. The second temperature environment is higher than the first temperature environment, and the second speed is lower than the first speed.

[0007] Further, step S2 includes: Preheating and homogenization stage: Keep the mandrel stationary or in a restricted rotation state, and preheat the liquid metal working medium to 40℃~60℃; Film formation stage: The bearing bush is rotated relative to the mandrel at a speed of 500 rpm to 3000 rpm for 30 seconds to 2 minutes, so that the liquid metal working medium gradually forms a liquid metal polishing film in the working gap.

[0008] Further, step S3 includes: The liquid metal working medium is heated to 60℃~80℃, and the bearing speed is increased to 3000rpm~10000rpm. The nano-abrasive particles are controlled at a first preset concentration, so that a dynamic pressure field is formed between the liquid metal polishing film and the outer surface of the mandrel. Under the action of the dynamic pressure field, the nano-abrasive particles migrate to the outer surface of the mandrel and the edge area of ​​the guide groove and apply a normal load to perform rough finishing on the outer surface of the mandrel and the edge area of ​​the guide groove. The bearing speed is reduced to 1000rpm~8000rpm, and the nano-abrasive particles are controlled to a second preset concentration less than the first preset concentration, so as to reduce the material removal rate of the nano-abrasive particles on the outer surface of the mandrel and the edge of the guide groove and improve the surface integrity of the outer surface of the mandrel and the edge of the guide groove, and perform fine finishing on the outer surface of the mandrel and the edge area of ​​the guide groove.

[0009] Furthermore, in step S3, the depth of the guide groove, the width of the guide groove, the size of the working gap, and the target removal amount are all positively correlated with the bearing rotation speed. The bearing rotation speed, the amount of liquid metal working medium filled, the abrasive concentration, and the working temperature are all positively correlated with the pressure field, velocity field, and temperature field of the liquid metal polishing film.

[0010] Furthermore, in step S4, under the temperature conditions of 40℃~60℃, abrasive-free liquid metal working medium is introduced into one end of the working gap at a flow rate of 0.1mL / min~50mL / min, so that the abrasive-free liquid metal working medium flows along the working gap, the inside of the guide groove and the bearing friction interface, so as to discharge the free abrasive particles, detached particles, abrasive residues and metal debris generated in step S2 at the other end of the working gap, thereby achieving the flushing of the outer surface of the mandrel and the inner surface of the bearing bush.

[0011] Further, step S5 includes: Contact interface formation stage: Keep the bearing stationary or rotate at a low speed of 10 rpm to 500 rpm, and heat it to 80 ℃ to 120 ℃ at a heating rate of 1 ℃ / min to 5 ℃ / min, and hold it at that temperature for 5 min to 60 min, so that the liquid metal working medium wets the outer surface of the mandrel and forms a continuous contact interface. Functional film formation stage: The temperature is continuously raised to 120℃~200℃ and held for 60min~180min, so that the liquid metal working medium and the outer surface of the mandrel undergo diffusion reaction or interface reaction to form a functional film.

[0012] Furthermore, step S5 also includes: After the functional film is formed, the bearing is kept stationary or rotated at a low speed of 10 rpm to 2000 rpm, and cooled to 120 ℃ to 150 ℃ at a cooling rate of 1 ℃ / min to 3 ℃ / min, and held at that temperature for 5 min to 90 min, so that the functional film grows uniformly along the circumference and axial direction of the core shaft.

[0013] Furthermore, the liquid metal working medium is gallium-based liquid metal; the nano-abrasives are one or more of nanodiamond abrasives, alumina abrasives, silicon carbide abrasives, and silicon dioxide abrasives. Steps S1 to S5 are all performed under an inert gas protective atmosphere, which is one or more of argon, nitrogen, or helium, used to reduce or avoid oxidation of the liquid metal working medium during processing.

[0014] In addition, the present invention also provides an integrated polishing and film-forming processing apparatus for liquid metal bearings, employing any of the integrated polishing and film-forming processing methods for liquid metal bearings described above, the apparatus comprising: A bearing support assembly includes a housing, the housing having a machining cavity, an airflow channel, and a liquid flow channel; the machining cavity is used to accommodate a liquid metal bearing; the airflow channel is connected to the machining cavity and is used to introduce an inert protective gas into the machining cavity; the liquid flow channel is connected to the working gap and is used to introduce a liquid metal working medium and nano-abrasive particles into the working gap and discharge waste material from the working gap. A drive assembly, disposed within the machining cavity and surrounding the bearing bush, is used to drive the bearing bush to rotate relative to the mandrel; A temperature control component, connected to the housing, is used to regulate and control the working temperature of the liquid metal working medium within the working gap.

[0015] Furthermore, the bearing support assembly also includes: A support base, located outside the housing, is used to support the housing. End seals, located on opposite sides of the housing, are used to prevent leakage of the liquid metal working medium from both ends of the mandrel.

[0016] This invention provides an integrated polishing and film-forming method and apparatus for liquid metal bearings. The method involves injecting a liquid metal working medium containing nano-abrasive particles into the working gap, causing the liquid metal working medium to form a liquid metal polishing film within the working gap. This liquid metal polishing film drives the nano-abrasive particles to polish and remove impurities from the outer surface of the mandrel and the edge of the guide groove, performing micro-polishing and micro-shaping. This application injects a liquid metal working medium doped with nano-abrasive particles into the working gap between the mandrel and the bearing bush, utilizing the gap fluid to form a stable liquid metal polishing film, and relying on the nano-abrasive particles to achieve flexible precision machining, simultaneously achieving surface polishing and herringbone groove micro-shaping. This application achieves residue-free clean processing through step-by-step medium replacement, using only the same liquid metal medium as the bearing throughout the process, without the introduction of any foreign heterogeneous media. After processing, there are no internal impurities, ensuring high cleanliness of the bearing working gap, the inside of the guide groove, and the friction interface, reducing abrasive wear during bearing operation. Step-by-step medium replacement achieves residue-free clean processing and reduces foreign contaminants. This invention utilizes the bearing's own liquid metal working medium throughout the entire processing, avoiding contamination problems caused by residual media from different processes and abrasive impurities. The media used in this invention are the bearing's native working medium under service conditions. After processing, there is no need for complete evacuation and replacement; the pure liquid metal can be directly retained in the bearing clearance as a lubricating medium, eliminating the need for additional lubricating materials. This results in high media utilization and low loss. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort. In the drawings, the same parts use the same reference numerals. The drawings are not drawn to scale.

[0018] Figure 1 This is a schematic flowchart of an embodiment of an integrated polishing and film-forming method for liquid metal bearings according to the present invention; Figure 2 This is a schematic diagram of the liquid metal bearing in this invention from one perspective; Figure 3 This is a three-dimensional schematic diagram of the mandrel of the liquid metal bearing in this invention; Figure 4 This is a perspective view of an embodiment of the integrated polishing and film forming processing apparatus of the present invention; Figure 5 This is a partial schematic diagram of an embodiment of the integrated polishing and film forming apparatus of the present invention; Figure 6This is a partial schematic diagram of another embodiment of the integrated polishing and film forming apparatus of the present invention; Figure 7 This is a schematic diagram of an embodiment of the integrated polishing and film forming processing device of the present invention connected to a liquid metal storage tank and a liquid metal replacement treatment tank; Figure 8 This is a schematic diagram of the outer surface of the mandrel in this invention before polishing and shaping. Figure 9 This is a schematic diagram of the outer surface of the mandrel after polishing and shaping in this invention; Figure 10 This is a partial schematic diagram of the liquid metal bearing in which the functional film layer is formed in this invention.

[0019] Key component symbols: 100 - Integrated polishing and film forming processing device; 110 - Bearing support assembly; 111 - Housing; 1111 - Processing chamber; 1112 - Air inlet; 1113 - Exhaust port; 1114 - Liquid inlet; 1115 - Liquid outlet; 112 - Support base; 113 - End seal; 120 - Drive assembly; 130 - Temperature control assembly; 101 - Mandrel; 102 - Bearing bush; 103 - Flow guide groove; 104 - Working gap; 105 - Liquid metal working medium; 106 - Functional film layer; 107 - Liquid inlet check valve; 108 - Liquid outlet check valve; 201 - Liquid metal storage tank; 202 - Liquid metal replacement and processing tank. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is referred to as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0022] It should also be noted that if the embodiments of the present invention involve directional indications, such as up, down, left, right, front, back, etc., these directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly. Furthermore, if the embodiments of the present invention involve descriptions such as "first," "second," "S1," "S2," "step one," "step two," etc., these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance, or implicitly indicating the number of technical features indicated or the order of method execution. Those skilled in the art will understand that anything that does not violate the inventive concept and does not contradict the inventive points should be included within the scope of protection of the present invention.

[0023] like Figure 1 As shown, this invention provides an integrated polishing and film-forming method for liquid metal bearings, which can be used to process materials such as... Figure 2 , Figure 3 The liquid metal bearing shown includes a spindle 101 and a bearing bush 102 sleeved on the outside of the spindle 101; a guide groove 103 is provided on the outer surface of the spindle 101; and a working gap 104 is formed between the spindle and the bearing bush.

[0024] In this embodiment, the method may optionally employ methods such as Figure 4 and Figure 5 The liquid metal bearing integrated polishing and film forming processing device 100 shown includes: a bearing support assembly 110, a drive assembly 120, and a temperature control assembly 130.

[0025] The bearing support assembly includes a housing, the housing having a machining cavity, an airflow channel, and a fluid flow channel; The machining cavity is used to accommodate the liquid metal bearing; The airflow channel is connected to the machining chamber and is used to introduce inert protective gas into the machining chamber to form an oxygen-free or low-oxygen protective environment around the mandrel 101 and the bearing 102. The liquid flow channel is connected to the working gap and is used to introduce liquid metal working medium and nano-abrasive particles into the working gap and discharge waste material in the working gap.

[0026] Additionally, the drive assembly 120 is disposed within the machining cavity 1111 and surrounds the bearing bush 102, for driving the bearing bush 102 to rotate relative to the spindle 101. Optionally, the drive assembly may be, for example, a drive coil. In this embodiment, the temperature control assembly 130 is connected to the bearing support assembly 110 and is used to regulate and control the working temperature of the liquid metal working medium within the working gap 104.

[0027] In this embodiment, as Figures 4 to 7As shown, the temperature control component 130 is located at the lower end of the outer peripheral surface of the housing 111. The temperature control component is, for example, a heating temperature control system, which heats the ambient temperature inside the processing cavity 1111 through an induction heating coil and monitors the temperature through a temperature sensor to achieve temperature regulation.

[0028] Specifically, such as Figure 5 and Figure 6 As shown, specifically, the mandrel is supported at both ends on the housing so that the bearing bush is suspended in a state without contact with the housing. In this embodiment, an air inlet 1112 and an exhaust outlet 1113 are provided at the upper end of the outer peripheral surface of the housing 111. The air inlet 1112, the machining chamber 1111, and the exhaust outlet 1113 are sequentially connected to form an airflow channel. The air inlet 1112 is used to introduce inert protective gas into the machining chamber, and the exhaust outlet 1113 is used to discharge the gas in the machining chamber to maintain the machining area in an oxygen-free or low-oxygen state.

[0029] Optionally, such as Figure 5 , Figure 6 and Figure 7 As shown, the housing also includes a liquid inlet 1114 and a liquid outlet 1115, a first detachable pipe connecting the working gap and the liquid inlet, and a second detachable pipe connecting the working gap and the liquid outlet. The liquid inlet, the first pipe, the working gap, the second pipe, and the liquid outlet are sequentially connected to form a liquid flow channel. Specifically, the liquid inlet 1114 is located at the bottom of the housing 111, and the liquid outlet 1115 is located at the top of the housing 111. The liquid inlet 1114 is connected to a submersible pump in the liquid metal storage tank 201 for injecting liquid metal working medium, and the liquid outlet 1115 is connected to the liquid metal replacement and treatment tank 202 for allowing excess liquid metal to flow into this area.

[0030] Optionally, such as Figure 5 , Figure 6 and Figure 7 As shown, a liquid inlet check valve 107 is provided on the bearing bush 102 corresponding to the liquid inlet 1114, and a liquid outlet check valve 108 is provided corresponding to the liquid outlet 1115. The liquid inlet check valve 107 and the liquid outlet check valve 108 are respectively located at both axial ends of the bearing bush 102. Specifically, when it is necessary to introduce liquid metal working medium containing or without nano-abrasive particles into the working gap, the first pipeline connects the liquid inlet 1114 and the liquid inlet check valve 107, and connects to the liquid metal storage tank 201 through the liquid inlet, thereby injecting the required liquid metal working medium into the working gap. Similarly, the second pipeline connects the liquid outlet 1115 and the liquid outlet check valve 108, and connects to the liquid metal replacement treatment tank 202 through the liquid outlet, thereby discharging excess liquid metal working medium or residual impurities from the working gap. This embodiment avoids backflow of the liquid metal working medium by setting up the liquid inlet check valve and the liquid outlet check valve.

[0031] Optionally, the bearing support assembly 110 also includes an inlet bolt cover and an outlet bolt cover. The inlet bolt cover is used to seal the inlet after the medium is injected during the working interval, and the outlet bolt cover is used to seal the outlet after the medium and impurities are discharged during the working interval, so as to prevent gas leakage in the processing chamber.

[0032] Optionally, the bearing support assembly 110 in this embodiment also includes a support base 112 and an end seal 113.

[0033] like Figures 4 to 7 As shown, in this embodiment, the support base 112 is disposed on opposite sides of the outer side of the housing 111 and is disposed at both ends of the spindle 101 to support the housing 111 so that the housing 111 is suspended.

[0034] In this embodiment, the end seals 113 are disposed at both ends of the mandrel 101 to prevent leakage of the liquid metal working medium. Optionally, the end seals in this embodiment may be, for example, sealing caps, which provide contact sealing to the ends of the mandrel. The sealing caps and the ends of the mandrel can be further sealed by adding sealing rings to further enhance their sealing performance, prevent leakage of the liquid metal working medium, and further enhance the sealing performance of the machining cavity.

[0035] like Figure 1 As shown, in this embodiment, the integrated polishing and film formation method for liquid metal bearings includes: S1: Introduce a liquid metal working medium containing a preset concentration of nano-abrasive particles into the working gap.

[0036] Specifically, the liquid metal bearing is placed in the machining chamber of the housing, with both ends of the mandrel mounted on the housing. Inert protective gas is introduced into the housing's air inlet, while the gas in the machining chamber is discharged from the housing's exhaust port. This creates an oxygen-free or low-oxygen protective environment around the mandrel and bearing bush under the inert gas protective atmosphere. Under this atmosphere, a liquid metal working medium containing nano-abrasive particles is injected into the working gap between the mandrel and bearing bush through the liquid inlet and a one-way valve.

[0037] In other embodiments, the liquid metal bearing can be introduced into a liquid metal working medium containing a preset concentration of nano-abrasive particles under an external inert gas protective atmosphere. After the introduction is completed, the liquid metal bearing is placed into the machining cavity of the housing and proceeds to step S2.

[0038] In this embodiment, the liquid metal working medium is, for example, gallium-based liquid metal, and the nano-abrasives are, for example, one or more of nanodiamond abrasives, alumina abrasives, silicon carbide abrasives, and silicon dioxide abrasives. Furthermore, the inert gas protective atmosphere in this embodiment is, for example, one or more of argon, nitrogen, or helium. This embodiment reduces or avoids oxidation of the liquid metal working medium during processing by using an inert gas protective atmosphere.

[0039] S2: Under the first temperature environment, the bearing bush is rotated relative to the spindle at the first speed, so that the liquid metal working medium forms a liquid metal polishing film in the working gap.

[0040] The purpose of step S2 is to utilize a relatively low-temperature, low-speed environment, compared to the subsequent substantial polishing and shaping steps, to gradually transform the liquid metal working medium within the working gap from its initial filled state to a stable, load-bearing liquid metal polishing film state. This prevents nano-abrasive particles from causing localized scratches on the outer surface of the mandrel in the unformed state. While this step may seem simple, it is crucial for the subsequent substantial polishing process. It enables the formation of a uniform liquid metal polishing film within the working gap, establishing a continuous film layer and a stable flow field. The absence of this liquid metal polishing film step will lead to the failure of subsequent polishing and shaping, resulting in a rough, uneven surface. For liquid metal bearings, especially in CT tubes used in medical diagnostics, even slight roughness or unevenness can significantly reduce medical image output, the lifespan of the CT scanner, and its effectiveness, causing substantial losses and harm due to misdiagnosis and missed diagnoses.

[0041] Since this stage does not aim for a high material removal rate, a relatively low temperature and a low bearing rotation speed are used. It is worth noting that the specific control of the temperature and rotation speed in this step to enable the liquid working medium to form a liquid metal polishing film within the working gap is not limited to the preferred embodiments described below.

[0042] In a preferred embodiment, step S2 is divided into two stages: a preheating and homogenization stage and a film-forming stage. The staged control makes the formation of the liquid metal polishing film more uniform and stable.

[0043] Specifically, the mandrel is first kept stationary or in a restricted rotational state. The liquid metal working medium containing nano-abrasive particles is preheated to 40℃~60℃ by a temperature control component. Then, the drive coil surrounding the outer side of the bearing is powered on to drive the bearing to rotate relative to the mandrel. The bearing rotates relative to the mandrel at a speed of 500rpm~3000rpm, which can be selected as 500rpm, 1000rpm or 3000rpm, for 30s~2min, which can be selected as 30s, 1min or 2min. This allows the liquid metal working medium to gradually form a stable liquid metal polishing film and pressure field within the working gap.

[0044] S3: Increase the temperature and speed up the process, so that the liquid metal polishing film, together with nano-abrasives, polishes and shapes the outer surface of the mandrel and the edge of the guide groove.

[0045] Specifically, after step S2, where a liquid metal working medium containing a preset concentration of nano-abrasive particles forms a liquid metal polishing film within the working gap, step S3 involves increasing the temperature and speed to allow the liquid metal polishing film, in conjunction with the nano-abrasive particles, to perform a polishing and shaping process on the outer surface of the mandrel and the edge of the guide groove. For example... Figure 8 and Figure 9 As shown, the dynamic pressure effect generated by the liquid metal polishing film creates a pressure field, which in turn drives nano-abrasive particles to polish and remove impurities and micro-shape the outer surface of the mandrel and the edge of the guide groove 103. For example, the polishing and shaping includes removing burrs, sharp corners, rough peaks, or micro-defects from the edge of the guide groove 103, transforming the edge of the guide groove 103 from a sharp state to a smooth transition state. Optionally, the guide groove in this embodiment is, for example, a herringbone groove.

[0046] More specifically, during the rotation of the bearing relative to the mandrel, the liquid metal polishing film creates a dynamic pressure field between the film and the mandrel surface due to the hydrodynamic effect within the working gap. This dynamic pressure field acts on the nano-abrasive particles suspended in the liquid metal working medium, causing them to migrate towards the outer surface of the mandrel and the edge region of the guide groove, thus applying a normal load. For example... Figure 8 and Figure 9 As shown, under the shear flow of the liquid metal working medium, the nano-abrasive particles produce a combination of micro-cutting, rolling and wiping effects on the outer surface of the mandrel and the edge area of ​​the guide groove 103 to remove machining marks, rough peaks, micro-protrusions and micro-cracks on the outer surface of the mandrel, and remove micro-defects such as burrs, sharp corners and chipped edges on the edge of the guide groove 103, thereby achieving uniform polishing removal of the outer surface of the mandrel and smooth shaping of the edge contour of the guide groove 103.

[0047] In a preferred embodiment, step S3 may include two stages: a roughing stage and a fineing stage, which facilitates controllable micro-shaping of the guide groove edge. Specifically, in the roughing stage, the bearing rotation speed can be increased to 3000 rpm to 10000 rpm, optionally 3000 rpm, 6000 rpm, 8000 rpm, or 10000 rpm, and the temperature of the liquid metal working medium can be controlled at 60℃ to 80℃, with a processing time of 3 min to 120 min, optionally 3 min, 10 min, 60 min, or 120 min. The mass fraction of the nano-abrasive particles in the liquid metal working medium can be 0.05 wt% to 5 wt%, optionally 0.05 wt%, 0.1 wt%, 2 wt%, or 5 wt%.

[0048] Furthermore, during the finishing stage, the bearing rotation speed can be controlled between 1000 rpm and 8000 rpm, preferably 1000 rpm, 3000 rpm, 6000 rpm, or 8000 rpm, and the processing time can be between 3 min and 60 min, preferably 10 min to 30 min. During the finishing stage, the material removal rate can be reduced and the surface integrity of the mandrel outer surface and the guide groove edge can be improved by reducing the mass fraction of nano-abrasive particles in the liquid metal working medium or shortening the processing time. Optionally, the mass fraction of nano-abrasive particles can be reduced to 0.01 wt% to 0.5 wt%.

[0049] This embodiment utilizes nano-abrasives to achieve flexible precision machining, combining surface polishing with micro-shaping of the guide groove. In this embodiment, a liquid metal working medium doped with nano-abrasives is injected into the working gap between the mandrel and the bearing bush. A stable liquid metal polishing film is formed using the gap fluid. The fluid viscosity drives the nano-abrasives to continuously perform micro-cutting and polishing on the outer surface of the mandrel, efficiently removing machining marks and protrusions from the substrate surface, significantly reducing surface roughness. Simultaneously, utilizing the ultra-fine particle size of the nano-abrasives, micro-shaping is performed on the edges of the guide groove, gently removing burrs, sharp corners, rough peaks, or micro-defects at the groove opening. This optimizes the edge morphology of the guide groove without damaging the overall groove structure, improving the groove contour accuracy, enhancing the hydrodynamic pressure accumulation effect, and effectively improving the bearing lubrication and load-bearing performance. These two-stage roughing and fine-shaping steps, by further controlling the temperature, rotation speed, and nano-abrasive concentration, achieve more precise and controllable shaping, further improving the shaping effect and product quality.

[0050] It should be noted that during step S3, the pressure field, velocity field and temperature field of the liquid metal polishing film can be controlled by adjusting at least one of the parameters of bearing rotation speed, liquid metal working medium filling amount, abrasive concentration and working temperature, thereby changing the migration state and intensity of nano-abrasives on the outer surface of the mandrel and the edge region of the guide groove.

[0051] The concentration of nano-abrasive particles can be adjusted according to the depth and width of the guide channel. For guide channels with a small depth or narrow width, a lower abrasive particle concentration of 0.01wt% to 0.5wt% can be used to avoid excessive rounding of the channel opening. For medium-sized guide channels, an abrasive particle concentration of 0.05wt% to 2wt% can be used to balance material removal efficiency and channel shape retention. For guide channels with a large depth or wide width, an abrasive particle concentration of 0.1wt% to 5wt% can be used, combined with a higher bearing speed or a stepped speed increase method, to enhance the polishing and shaping effect of the nano-abrasive particles on the bottom and opening areas of the channel.

[0052] Specifically, as the bearing speed increases, the shearing and dynamic pressure effects of the liquid metal working medium within the working gap are enhanced, and the bearing pressure and abrasive carrying capacity of the liquid metal polishing film are correspondingly increased. When the filling amount of the liquid metal working medium increases, the medium renewal effect within the working gap and the guide groove can be enhanced, allowing chips, detached particles, and locally agglomerated abrasive particles generated during processing to leave the bottom and opening of the groove in a timely manner and migrate towards the outlet with the flow of the liquid metal working medium. This reduces the risk of local particle accumulation, secondary scratches, and uneven processing, and is mainly used to maintain a stable processing state during the polishing and shaping stage. When the working temperature increases, the fluidity of the liquid metal working medium increases, which is conducive to the formation of a continuous and stable polishing film within the working gap and the guide groove.

[0053] Furthermore, the bearing rotation speed can be selected or adjusted in stages according to the depth and width of the guide groove, the working clearance, the abrasive concentration, and the target removal amount.

[0054] Specifically, for guide channels with shallow depths or narrow widths, lower rotational speeds and shorter processing times can be used, such as 1000 rpm to 3000 rpm for bearing speeds and 3 to 30 minutes for processing time, to avoid excessive rounding of the channel opening or distortion of the channel profile. For medium-sized guide channels, medium rotational speeds can be used, such as 3000 rpm to 6000 rpm for bearing speeds and 10 to 60 minutes for processing time, to balance material removal efficiency and channel shape retention. For guide channels with deep depths or wide widths, higher rotational speeds or stepped speed increases can be used, such as 6000 rpm to 10000 rpm for bearing speeds and 10 to 120 minutes for processing time, to enhance the shear flow, abrasive transport, and media renewal of the liquid metal working medium in the channel bottom and opening areas. For deep and narrow guide channels, a medium rotation speed can be used, such as a bearing speed of 3000 rpm to 6000 rpm and a processing time of 10 min to 60 min, in order to enhance the disturbance effect of the liquid metal working medium inside the guide channel and reduce the risk of nano-abrasive particles being retained in the bottom or opening area of ​​the channel, local scratches, and distortion of the channel profile.

[0055] Specifically, when the working gap is small, the velocity gradient and shearing effect of the liquid metal working medium are stronger at the same bearing speed, and the effect of nano-abrasives on the outer surface of the mandrel and the edge of the guide groove is greater. Therefore, a lower bearing speed or a shorter processing time can be used, such as a bearing speed of 1000 rpm to 3000 rpm and a processing time of 3 min to 30 min, to avoid excessive removal in some areas, surface scratches, or excessive rounding of the groove. When the working gap is large, the shearing effect and dynamic pressure effect of the liquid metal working medium are relatively weakened at the same bearing speed. Therefore, a higher bearing speed, a longer processing time, or a stepped speed increase method can be used, such as a bearing speed of 6000 rpm to 10000 rpm and a processing time of 30 min to 120 min, to ensure the stability of the liquid metal polishing film and the effective effect of the abrasives.

[0056] When the abrasive concentration is high, a larger number of nano-abrasive particles participate in polishing and shaping, resulting in stronger material removal. Therefore, a lower bearing speed or shorter processing time can be used, such as a bearing speed of 1000 rpm to 3000 rpm and a processing time of 3 min to 30 min, to avoid excessive local removal or surface scratches. When the abrasive concentration is low, the material removal effect is relatively weaker. Therefore, a medium to high bearing speed or a longer processing time can be used, such as a bearing speed of 3000 rpm to 10000 rpm and a processing time of 30 min to 120 min, to ensure polishing and shaping efficiency.

[0057] When the target removal amount is large, a higher bearing speed, a longer processing time, or a phased speed increase method can be used, such as a bearing speed of 6000rpm~10000rpm and a processing time of 30min~120min, to improve the material removal efficiency. When the target removal amount is small, a lower bearing speed, a shorter processing time, or a lower abrasive concentration can be used, such as a bearing speed of 1000rpm~3000rpm and a processing time of 3min~30min, to reduce the material removal rate and avoid excessive changes in the outer diameter of the mandrel or distortion of the guide groove profile.

[0058] S4: Stops the bearing bush from rotating and introduces a non-abrasive liquid metal working medium into the working gap to clean the inside of the bearing.

[0059] Specifically, after polishing and shaping are completed, the drive assembly gradually stops the rotation of the bearing bush, and aligns the liquid inlet check valve on the bearing bush with the liquid inlet on the housing, and the liquid outlet check valve on the bearing bush with the liquid outlet on the housing. Under an inert gas protective atmosphere, abrasive-free liquid metal working medium is introduced into the working gap through the liquid inlet and the liquid inlet check valve. The abrasive-free liquid metal working medium flows along the working gap, the inside of the guide groove, and the bearing friction interface, and washes the outer surface of the mandrel and the inner surface of the bearing bush. Excess medium and residual impurities are discharged to the liquid metal replacement treatment tank through the liquid outlet check valve and the liquid outlet. The temperature of the abrasive-free liquid metal working medium can be 40℃~60℃, the flow rate can be 0.1mL / min~50mL / min, preferably 0.5mL / min~20mL / min, and the replacement time can be 1min~20min, so as to remove free abrasive particles, detached particles, abrasive residues and metal debris generated during the polishing process, thereby improving the cleanliness of the working gap, the inside of the guide groove and the bearing friction interface.

[0060] In other embodiments, the bearing can be removed from the integrated polishing and film forming apparatus and placed under an external inert gas protective atmosphere. The outer surface of the mandrel and the inner surface of the bearing bush are rinsed with a non-abrasive liquid metal working medium. After rinsing, the liquid metal bearing is placed into the processing cavity of the housing and proceeds to step S5.

[0061] This embodiment first utilizes a polishing and shaping process using a nano-abrasive medium, followed by the introduction of a pure, abrasive-free liquid metal working medium for gap flushing and cleaning. This efficiently replaces and removes residual free abrasive particles, microscopic chips, and other impurities from the gaps. Throughout the entire process, only bearing-derived liquid metal media is used, with no foreign media introduced. This ensures no internal impurities remain after processing, guaranteeing high cleanliness of the bearing's working gaps, the interior of the guide grooves, and the friction interface. This reduces abrasive wear during bearing operation, and the step-by-step media replacement achieves residue-free clean processing, minimizing foreign contaminants.

[0062] S5: In the second temperature environment, the bearing is rotated relative to the spindle at a second speed, so that the liquid metal working medium 105 reacts with the outer surface of the spindle in situ to form a functional film layer 106; the second temperature environment is higher than the first temperature environment, and the second speed is lower than the first speed.

[0063] After rinsing the working gap, the inner surface of the bearing bush, and the outer surface of the spindle, a non-abrasive liquid metal working medium is continuously injected into the working gap, and this non-abrasive liquid metal working medium is retained in the clean working gap.

[0064] In this embodiment, the outer surface of the mandrel 101 includes a molybdenum-based material surface. Step S5 includes a film formation preheating stage, a gallium-molybdenum interface reaction stage, a film homogenization stage, and a protective cooling stage. Step S5 in this embodiment, through staged control, enables the abrasive-free liquid metal working medium to form a stable wetting contact interface on the outer surface of the mandrel, and makes the interfacial diffusion reaction between the gallium-based liquid metal and the molybdenum-based material more uniform.

[0065] like Figure 10 As shown, in step S5, the ambient temperature inside the processing cavity is controlled in stages by the temperature control component, so that the liquid metal working medium 105 in the working gap 104 reaches the preset film-forming conditions and undergoes an in-situ interface reaction with the molybdenum-based material on the outer surface of the mandrel 101, thereby forming a functional film layer 106 on the outer surface of the mandrel 101.

[0066] Specifically, during the film-forming preheating stage, the temperature of the processing chamber can be raised to 80℃~120℃ at a rate of 1℃ / min~5℃ / min and held for 5min~60min. During this stage, the bearing can remain stationary or rotate continuously or intermittently at a speed of 10rpm~500rpm to promote the full wetting of the outer surface of the mandrel by the liquid metal working medium and improve the uniformity of temperature distribution.

[0067] During the gallium-molybdenum interface reaction stage, the temperature can be further increased to 120°C to 200°C, which can be selected as 120°C, 160°C or 200°C, and held for 60 min to 180 min, preferably 60 min, 120 min or 180 min. During this stage, the bearing can be kept stationary, or rotated continuously or intermittently at a speed of 10 rpm to 1000 rpm, so as to continuously renew the liquid metal working medium near the outer surface of the mandrel, promote the uniform diffusion reaction or interface reaction between the gallium-based liquid metal and the surface of the molybdenum-based material, and form a dense, continuous functional film layer with wettability and / or corrosion resistance. This functional film layer 106 is, for example, a molybdenum-gallium intermetallic compound.

[0068] Specifically, after the film layer is formed, a film homogenization stage can be further entered. This involves maintaining the temperature at the interface reaction temperature or 120℃~150℃ for 5min~90min, while the bearing is continuously or intermittently rotated at a low speed of 10rpm~2000rpm to continuously renew the liquid metal working medium near the outer surface of the mandrel. This promotes uniform growth of the functional film layer along the circumferential and axial directions of the mandrel, improving the thickness consistency and interfacial bonding stability of the functional film layer. Subsequently, during the protective cooling stage, an inert gas protective atmosphere is maintained, and the liquid metal bearing is cooled to below 60℃ at a cooling rate of 1℃ / min~20℃ / min to reduce the oxidation risk of the gallium-based liquid metal working medium and the gallium-molybdenum reaction film layer during the cooling process. The resulting functional film layer has high bonding strength and good continuity, and also has good surface wettability and corrosion resistance. It can improve the spreading ability of liquid metal working medium at the bearing friction interface and enhance the stability of lubricating film formation. It can also isolate air and corrosive media and inhibit the oxidation and corrosion of the spindle substrate, thereby improving the service reliability and service life of liquid metal bearings under high temperature or extreme working conditions.

[0069] In this embodiment, a preferred embodiment of step S5 is provided. Under low-speed rotation and slow heating, gallium is uniformly spread and wetted on the molybdenum surface, promoting the full wetting of the outer surface of the mandrel by the liquid metal working medium and improving the uniformity of temperature distribution, forming a large-area, continuous contact interface, rather than isolated point contacts. This provides thermodynamic driving force for subsequent interface diffusion and reaction, shortening the "latency period" of the interface reaction. This step, though seemingly simple, is crucial for the subsequent formation of the functional film. A continuous contact interface is a prerequisite for the full diffusion reaction of gallium-molybdenum to generate the target film. Only when the initial contact is sufficiently uniform and continuous can the subsequent interface reaction proceed uniformly, ultimately obtaining a film with consistent performance. If this preheating stage for film formation is missing, the subsequent formation of the functional film will fail, easily leading to film cracking or bearing substrate deformation, failing to guarantee the structural integrity of the functional film, and failing to meet the operating conditions of the liquid metal bearing. Especially for CT tubes used in medical diagnosis, this will greatly reduce medical image output, the service life and effectiveness of the CT machine, and cause significant losses and harms such as misdiagnosis and missed diagnosis.

[0070] Under sustained high temperature and low speed rotation, sufficient thermodynamic driving force and kinetic time are provided for the diffusion or interfacial reaction between gallium and molybdenum. At high temperatures, atomic mobility is significantly increased, promoting uniform diffusion or interfacial reactions between the gallium-based liquid metal and the molybdenum-based material surface. The micro-shear force generated by low-speed rotation helps to expel bubbles, pores, and oxide inclusions from within the film layer, causing the film structure to change from loose to dense, forming a dense, continuous functional film layer with wettability and / or corrosion resistance. For bearing applications, good wettability means that the functional film layer can form a better interfacial bond with the lubricating medium during subsequent use, reducing interfacial thermal resistance and frictional resistance. Holding at high temperature for a period of time allows the functional film layer to grow uniformly along the axial direction of the mandrel during low-speed rotation, forming a more uniform and stable functional film layer, further improving the overall quality and lifespan of the liquid metal bearing. Especially when applied to high-precision equipment such as CT tubes, it significantly extends bearing life, reduces the frequency of CT tube replacement, and ensures rotational accuracy and image quality at high speeds.

[0071] It is noteworthy that the integrated polishing and film-forming processing method for liquid metal bearings of this invention utilizes the bearing's own liquid metal working medium throughout the entire process, avoiding contamination problems caused by residual media from different processes and abrasive impurities. The media used in this invention are the original working media under the bearing's service conditions. After processing, there is no need for complete emptying and replacement; the pure liquid metal can be directly retained in the bearing gap as a lubricating medium, eliminating the need for additional lubricating materials. This results in high media utilization and low loss. This invention uses the liquid metal bearing working medium simultaneously as a polishing medium, a shaping medium, and a film-forming reaction medium, reducing heterogeneous contamination and improving bearing surface precision, guide groove edge quality, and interfacial functional film preparation efficiency. It is suitable for precision and clean processing of high-temperature liquid metal bearings. This invention completes all polishing, shaping, cleaning, and film-forming processes sequentially within the same device, eliminating the need for bearing disassembly and secondary clamping, and avoiding positioning errors caused by multiple clamping operations. This integrated and continuous processing mode significantly shortens the processing flow and reduces processing time.

[0072] The embodiments described above are merely examples 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. 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 modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An integrated polishing and film-forming method for liquid metal bearings, characterized in that, The liquid metal bearing includes a mandrel, a bearing bush sleeved on the outside of the mandrel and rotatable around the mandrel, a working clearance between the mandrel and the bearing bush, and a guide groove on the outer surface of the mandrel; the method includes: S1: Introduce a liquid metal working medium containing a preset concentration of nano-abrasive particles into the working gap; S2: Under a first temperature environment, the bearing is rotated relative to the mandrel at a first rotation speed, so that the liquid metal working medium forms a liquid metal polishing film in the working gap; including: preheating and homogenization stage: keeping the mandrel stationary and preheating the liquid metal working medium to 40℃~60℃; film building stage: rotating the bearing relative to the mandrel at a rotation speed of 500rpm~3000rpm for 30s~2min, so that the liquid metal working medium gradually forms a liquid metal polishing film in the working gap; S3: Increased temperature and speed, allowing the liquid metal polishing film to work with nano-abrasives to polish and shape the outer surface of the mandrel and the edge of the guide groove; S4: Stop the bearing bush from rotating and introduce non-abrasive liquid metal working medium into the working gap to clean the inside of the bearing; S5: Under a second temperature environment, the bearing bush is rotated relative to the mandrel at a second rotation speed, causing the liquid metal working medium to undergo an in-situ interfacial reaction with the outer surface of the mandrel, forming a functional film layer; including: the contact interface formation stage: keeping the bearing bush stationary or rotating at a low speed of 10 rpm to 500 rpm, and heating it to 80℃ to 120℃ at a heating rate of 1℃ / min to 5℃ / min, and holding it at that temperature for 5 min to 60 min, so that the liquid metal working medium wets the outer surface of the mandrel, forming a continuous contact interface; the functional film layer formation stage: continuously heating it to 120℃ to 200℃, and holding it at that temperature for 60 min to 180 min, so that the liquid metal working medium undergoes a diffusion reaction or interfacial reaction with the outer surface of the mandrel, forming a functional film layer; The second temperature environment is higher than the first temperature environment, and the second speed is lower than the first speed.

2. The integrated polishing and film formation method for liquid metal bearings according to claim 1, characterized in that, Step S3 includes The liquid metal working medium is heated to 60℃~80℃, and the bearing speed is increased to 3000rpm~10000rpm. The nano-abrasive particles are controlled at a first preset concentration, so that a dynamic pressure field is formed between the liquid metal polishing film and the outer surface of the mandrel. Under the action of the dynamic pressure field, the nano-abrasive particles migrate to the outer surface of the mandrel and the edge area of ​​the guide groove and apply a normal load to perform rough finishing on the outer surface of the mandrel and the edge area of ​​the guide groove. The bearing speed is reduced to 1000rpm~8000rpm, and the nano-abrasive particles are controlled to a second preset concentration less than the first preset concentration, so as to reduce the material removal rate of the nano-abrasive particles on the outer surface of the mandrel and the edge of the guide groove and improve the surface integrity of the outer surface of the mandrel and the edge of the guide groove, and perform fine finishing on the outer surface of the mandrel and the edge area of ​​the guide groove.

3. The integrated polishing and film formation method for liquid metal bearings according to claim 2, characterized in that, In step S3, the depth of the guide groove, the width of the guide groove, the size of the working gap, and the target removal amount are all positively correlated with the bearing rotation speed. The bearing rotation speed, the amount of liquid metal working medium filled, the abrasive concentration, and the working temperature are all positively correlated with the pressure field, velocity field, and temperature field of the liquid metal polishing film.

4. The integrated polishing and film formation method for liquid metal bearings according to claim 1, characterized in that, In step S4, at a temperature of 40℃ to 60℃, a non-abrasive liquid metal working medium is introduced into one end of the working gap at a flow rate of 0.1 mL / min to 50 mL / min. The non-abrasive liquid metal working medium flows along the working gap, the inside of the guide groove, and the bearing friction interface, so as to discharge the free abrasive particles, detached particles, abrasive residues, and metal debris generated in step S2 at the other end of the working gap, thereby achieving the flushing of the outer surface of the mandrel and the inner surface of the bearing bush.

5. The integrated polishing and film formation method for liquid metal bearings according to claim 1, characterized in that, Step S5 also includes: After the functional film is formed, the bearing is kept stationary or rotated at a low speed of 10 rpm to 2000 rpm, and cooled to 120 ℃ to 150 ℃ at a cooling rate of 1 ℃ / min to 3 ℃ / min, and held at that temperature for 5 min to 90 min, so that the functional film grows uniformly along the circumference and axial direction of the core shaft.

6. The integrated polishing and film-forming method for liquid metal bearings according to claim 1, characterized in that, The liquid metal working medium is gallium-based liquid metal; the nano-abrasives are one or more of nanodiamond abrasives, alumina abrasives, silicon carbide abrasives, and silicon dioxide abrasives. Steps S1 to S5 are all performed under an inert gas protective atmosphere, which is one or more of argon, nitrogen, or helium, used to reduce or avoid oxidation of the liquid metal working medium during processing.

7. The integrated polishing and film-forming method for liquid metal bearings according to any one of claims 1 to 6, characterized in that, An integrated polishing and film-forming processing device is used; the device includes: A bearing support assembly includes a housing, the housing having a machining cavity, an airflow channel, and a liquid flow channel; the machining cavity is used to accommodate a liquid metal bearing; the airflow channel is connected to the machining cavity and is used to introduce an inert protective gas into the machining cavity; the liquid flow channel is connected to the working gap and is used to introduce a liquid metal working medium and nano-abrasive particles into the working gap and discharge waste material from the working gap. A drive assembly, disposed within the machining cavity and surrounding the bearing bush, is used to drive the bearing bush to rotate relative to the mandrel; A temperature control component, connected to the housing, is used to regulate and control the working temperature of the liquid metal working medium within the working gap.

8. The integrated polishing and film-forming method for liquid metal bearings according to claim 7, characterized in that, The bearing support assembly also includes: A support base, located outside the housing, is used to support the housing. End seals, located on opposite sides of the housing, are used to prevent leakage of the liquid metal working medium from both ends of the mandrel.

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