Method for monitoring metal migration in situ to realize intelligent lubrication characteristic

Abstract

The invention relates to a method for realizing intelligent lubrication characteristics by monitoring metal migration in situ. It is revealed that the lubrication rule in the dynamic friction process is the difficult point of lubricating material research, especially in the extreme space environment. The conventional online in-situ detection system has the problems of complex components and single detection signal. A mass spectrometer, a desk type universal meter and a vacuum friction testing machine are used as basic components, and gold / carbon nano composite and copper / carbon nano composite metal doped hard coatings are used as application objects. Physical and chemical signals of the metal / carbon composite film in the friction process in the extreme vacuum environment are synchronously monitored in situ through a mass spectrometer and a universal meter, and the dynamic lubrication behavior and the lubrication mechanism of the metal / carbon composite film in the friction process are analyzed according to the detected substance release amount signal and the detected electrical signal. And the change rule of the lubrication behavior and the signal feedback is mastered, so that lubrication regulation and control are further realized. According to the method, the problem that a dynamic lubrication mechanism is unknown due to the lack of a suitable in-situ characterization method in an extreme environment is solved.

Description

Technical Field

[0001] This invention belongs to the field of surface composition state detection and analysis technology, specifically relating to a method for in-situ monitoring of metal migration to achieve intelligent lubrication characteristics, which can be applied to real-time monitoring and mechanism research of lubrication behavior of lubricating films during friction. Background Technology

[0002] Friction and wear are among the leading causes of mechanical component failure, especially in high-end fields such as aerospace and precision equipment, where approximately 80% of mechanical failures are related to wear. To improve equipment reliability and extend service life, developing high-performance lubricating materials and elucidating their lubrication mechanisms is crucial. Among these, the ability to monitor the behavior of lubricating materials during dynamic friction processes in real or simulated service environments is key to revealing their lubrication mechanisms and achieving proactive performance control.

[0003] Currently, most studies on lubrication behavior rely on offline characterization after friction tests (such as scanning electron microscopy, surface topography, and energy dispersive spectroscopy). These methods cannot obtain dynamic evolution information on interface structure and chemical state during friction, making it difficult to fully reveal the lubrication and failure mechanisms of materials under real working conditions. Therefore, in-situ monitoring technology of the friction process has become an important development direction in this field.

[0004] Several existing technologies have been developed to achieve in-situ monitoring of the friction process, which can be broadly classified into two categories: One type of approach focuses on inferring surface morphology evolution through the fusion of multi-source physical signals. For example, the "Wear Morphology Reconstruction Method and System Based on Multi-Source Friction Information Fusion" (Patent Publication No. CN116992769A) proposed by Shanghai Jiao Tong University collects signals such as vibration, sound pressure, and sound, and establishes a correlation model between these signals and the characteristic parameters of the wear surface morphology, thereby achieving real-time reconstruction and visual monitoring of the wear morphology. However, this method mainly reflects the mechanical vibration and deformation information during the friction process, and it is difficult to detect key chemical processes such as chemical reactions and substance release occurring at the friction interface, thus limiting its ability to reveal the tribochemical mechanisms of lubricating materials.

[0005] Another approach focuses on directly monitoring changes in surface chemical state through spectroscopic methods. For example, the "Online In-situ Detection and Analysis System for Wear Failure Mechanism of Wide-Temperature-Range Lubricating Materials" (Patent Publication No. CN119394834A) proposed by the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, introduces in-situ Raman spectroscopy to achieve real-time analysis of the phase composition of friction surfaces under complex environments such as high temperature and vacuum, effectively revealing the tribochemical mechanisms of various materials, including organic and inorganic materials. However, this method relies on a single monitoring signal and is highly dependent on the Raman activity of the material. For metal-doped amorphous carbon-based materials such as gold and copper, where gold and copper nanoparticles lack Raman activity, this method is difficult to use effectively for detection.

[0006] Furthermore, in experiments simulating extreme service environments such as space stations and vacuum, the systems are typically under high vacuum or special atmospheric conditions, severely limiting the introduction of conventional characterization methods. Gold and copper-doped carbon nanocomposite films, as an important type of metal-doped hard lubricating coating, exhibit lubrication performance highly dependent on dynamic physical and chemical processes during friction, such as the migration of metal components and the formation and evolution of the friction interface transfer film. Current technologies lack multi-source information fusion monitoring methods capable of simultaneously and in-situ acquiring physical signals (such as conductivity and contact state) and chemical signals (such as reaction products and substance release) at the friction interface of such materials in extreme vacuum environments. This results in a lack of clarity regarding the lubrication mechanism of these materials in dynamic friction, particularly key processes such as interface self-healing and tribochemical evolution, severely restricting the optimization of material performance and engineering applications.

[0007] Therefore, there is an urgent need to develop an in-situ method suitable for extreme environments that can simultaneously monitor the physical state and chemical changes during friction, in order to reveal the true behavior and underlying mechanisms of lubricating materials such as metal / carbon nanocomposite films in dynamic friction. This invention is proposed against this background. Summary of the Invention

[0008] The present invention aims to provide a method for multi-signal in-situ synchronous monitoring of the lubrication behavior of carbon nanocomposite films doped with metals such as gold and copper, suitable for extreme vacuum environments, so as to reveal the physical and chemical evolution laws and lubrication mechanism during dynamic friction.

[0009] To address the aforementioned technical problems, this invention provides a method for in-situ monitoring of metal migration to achieve intelligent lubrication characteristics. The core of this method lies in constructing an in-situ monitoring system that integrates the ability to simultaneously acquire physical and chemical signals, and using multi-signal correlation analysis to elucidate lubrication behavior.

[0010] The method is based on the following system: This system uses a vacuum tribological testing machine as its core platform. A mass spectrometer is externally connected to its chamber via a flange port to monitor ion fragments (chemical signals) released during the tribological process. Simultaneously, the positive and negative leads of a benchtop multimeter are introduced into the chamber through the flange port and connected to the dual rod (and its end ball) and sample clamping module of the vacuum tribological testing machine, respectively, forming a complete electrical monitoring circuit for real-time monitoring of the resistance change (physical signal) of the tribological system. The metal / carbon nanocomposite thin film is preferably prepared by co-sputtering a metal target and a graphite target using magnetron sputtering technology, wherein the metal nanoparticles are uniformly doped into the amorphous carbon film in elemental form.

[0011] The method mainly includes the following steps: (1) System connection: The mass spectrometer is externally connected to the chamber of the vacuum friction testing machine via a flange port; The positive and negative leads of the benchtop multimeter are introduced into the chamber through flange ports, respectively; wherein, the positive lead is connected to the mating rod of the vacuum friction testing machine, and the end of the mating rod is equipped with a mating ball for performing the friction test; the negative lead is connected to the sample clamping module of the vacuum friction testing machine. (2) Sample installation and circuit construction: A sample coated with a metal / carbon nanocomposite film is mounted on the sample clamping module; the sample clamping module, the sample, the dual ball, and the dual rod together constitute a friction pair and an electrical monitoring circuit; Ensure that the mating rod is insulated from other moving components of the friction testing machine, and ensure that the specimen is in conductive contact with the specimen clamping module to form a complete electrical monitoring circuit; (3) Parameter setting and vacuum preparation: Set the load, frequency, and amplitude parameters for the friction test; Set the benchtop multimeter to resistance measurement mode; Set the acquisition parameters of the mass spectrometer; Evacuate the chamber to the target vacuum level; (4) Synchronous in-situ monitoring and data acquisition: When the vacuum level in the chamber is stable and the background impurity signal detected by the mass spectrometer drops to its lowest level, the friction test procedure is started. During the friction process, the friction coefficient signal is collected in real time by the vacuum friction testing machine, the resistance change signal of the friction pair is collected in real time by the benchtop multimeter, and the ion fragment signal released at the friction interface is collected in real time by the mass spectrometer. (5) Lubrication behavior analysis: Establish curves showing the changes in friction coefficient, resistance value, and ion fragment release amount over time; By analyzing the correspondence and linkage among the three factors in the aforementioned change curves, the lubrication behavior and mechanism of the metal / carbon nanocomposite film during dynamic friction are revealed.

[0012] As a preferred technical solution of the present invention: The friction test was conducted in a reciprocating mode with a test frequency of less than 6 Hz.

[0013] The mating rod adopts a segmented insulation design to ensure electrical insulation between it and the drive assembly of the vacuum friction testing machine.

[0014] The benchtop multimeter has a resistance measurement range of 1 GΩ and a resolution of 10 μΩ.

[0015] The mass spectrometer has a detection range of 1-200 u, a residence time of 1 ms-16 s / u, and a detection limit of 5 × 10⁻⁶. -19 mbar, vacuum level requirement below 10 -4 The vacuum level is in the mbar range, achieved by connecting a mechanical pump and a molecular pump in series.

[0016] The substrate material of the sample is a conductive substrate, and the material of the dual spheres is a conductive material.

[0017] The base material is 304 stainless steel, and the material of the mating ball is GCr15 bearing steel.

[0018] The metal / carbon nanocomposite film is a gold / carbon nanocomposite film or a copper / carbon nanocomposite film, prepared by co-sputtering a metal target and a graphite target using magnetron sputtering technology.

[0019] The ion fragment signal is the release intensity signal of gold ions with a mass-to-charge ratio of 197 or copper ions with a mass-to-charge ratio of 64.

[0020] The lubrication behavior includes at least one of the following: migration of metal nanoparticles, formation and evolution of transfer films, and interface self-healing behavior.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention, through the combined use of a mass spectrometer and a benchtop multimeter, achieves for the first time in-situ simultaneous monitoring of physical signals (resistance) and chemical signals (ion fragment release) during the friction process of metal / carbon nanocomposite thin films under extreme vacuum conditions. This breakthrough overcomes the dependence of traditional spectroscopic methods on the Raman activity of materials, making it particularly suitable for studying the mechanisms of such weakly / non-Raman-active metal-doped coatings. Through multi-signal correlation analysis, the migration and replenishment behavior of metal nanoparticles and the evolution of the carbon matrix during friction can be clearly revealed, thereby elucidating the dynamic lubrication state and interface self-healing mechanism of the thin film. This method features a simple system structure, good compatibility, and stable operation in extreme environments such as high vacuum. It provides a reliable means for in-depth understanding of the tribological behavior and failure mechanisms of such materials under real-world conditions, and has significant guiding significance for the research and performance optimization of high-performance solid lubricating materials. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the system device connection for the in-situ monitoring method described in this invention.

[0023] Figure 2 for Figure 1 Schematic diagram of the insulation design of the mating rod used in the medium vacuum friction testing machine.

[0024] Figure 3 This is a synchronous relationship curve of friction coefficient, system resistance, and gold release over time when testing gold / carbon nanocomposite thin films using the method of this invention.

[0025] Figure 4 This is a synchronous relationship curve of friction coefficient, system resistance, and copper release over time when testing copper / carbon nanocomposite thin films using the method of this invention.

[0026] Figure 5 To analyze the lubrication mechanism of copper / carbon nanocomposite films using in-situ Raman spectroscopy, the obtained friction coefficient and I D / I G A graph showing the synchronous relationship between the value and time.

[0027] In the diagram: 1- Benchtop multimeter; 2- Mass spectrometer; 3- Vacuum friction testing machine chamber; 4- Friction testing unit; 5- Computer monitor; 6- Molecular pump; 7- Motor; 8- Mechanical pump; 9- Air compressor; 10- Computer host; 11- Dual rod. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings, specific embodiments, and comparative examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation thereof.

[0029] Example 1: This embodiment uses the monitoring of the lubrication and self-healing behavior of gold / carbon nanocomposite thin films prepared by magnetron sputtering under extreme vacuum conditions as an example to illustrate the implementation process of the present invention in detail.

[0030] 1. System Connection according to Figure 1 The in-situ monitoring system is set up as shown. The mass spectrometer 2 is connected to the chamber 3 of the vacuum friction testing machine through the vacuum flange port. For the benchtop multimeter 1, two copper wires (with outer insulating ceramic sleeves) are used to connect its positive and negative terminals respectively, and the other ends of these two wires are introduced into the chamber 3 through the vacuum flange port, ready to be connected to the mating rod 11 and the friction clamping module respectively.

[0031] 2. Sample clamping The sample with the prepared gold / carbon nanocomposite thin film (substrate: 304 stainless steel, 1 mm thick) was mounted onto the sample clamping module of the vacuum tribometer. The mating balls were made of GCr15 bearing steel (6 mm diameter, roughness approximately 20 nm). The film surface and the mating ball surface were carefully wiped clean with a cotton ball soaked in anhydrous ethanol. The positive lead of the multimeter leading into the chamber was connected to the mating rod 11 via a metal screw, and the negative lead was connected to the clamping module. The clamping module was ensured to be in close contact with the back of the sample to form a complete electrical circuit: mating rod → mating ball → thin film → sample substrate → clamping module. Figure 2 As shown, the mating rod 11 adopts a segmented material design. The part that connects to the friction testing machine drive component (such as motor 7) must be insulated. A handheld multimeter is used to confirm that there is no electrical conductivity between the mating rod 11 and the friction assembly.

[0032] 3. Experimental Design and Parameter Setting To study the lubrication mechanism of thin films and their self-healing behavior after interface damage, the following scheme was designed: First, a steady-state friction was performed, then the dual spheres were removed and replaced with new dual spheres to disrupt the original friction interface. Subsequently, experiments were continued on the original wear marks, and the behavior was reflected by monitoring changes in resistance and mass spectrometry signals.

[0033] The friction test was set to reciprocating mode, with an amplitude of 5 mm, a frequency of 3 Hz, and a load of 1 N. The positions of the specimen and the mating rod were adjusted so that the mating ball was in contact with the specimen. Mechanical pump 8 and molecular pump 6 were started to evacuate chamber 3. When the vacuum level reached 2 × 10⁻⁶... -5At mbar, turn on mass spectrometer 2 and set its acquisition interval to 35.794 seconds. Set benchtop multimeter 1 to resistance measurement mode and set its acquisition interval to 0.362 seconds. Continuously monitor until the intensity of background impurity signals such as H2O detected by the mass spectrometer decreases and stabilizes at the lowest level (approximately 20 minutes), then prepare to begin the triboelectric test.

[0034] 4. Data Acquisition, Processing and Analysis Once the background signal stabilizes, the friction program is initiated, and the friction coefficient, resistance value, and mass spectrometry signal (release intensity of Au (mass-to-charge ratio 197)) are recorded simultaneously. After 480 seconds of friction, the friction reaches a stable state, at which point friction is paused and data acquisition is stopped. Subsequently, a new pair of balls is replaced, and the friction experiment is restarted at the original wear mark location, with the same parameters as in step 3. Once the friction coefficient decreases and stabilizes again (approximately 480 seconds later), all tests are stopped.

[0035] The collected data were processed: the Au release intensity per unit time was calculated. Data on the changes in friction coefficient, system resistance, CO release intensity, and Au release intensity over time were integrated and plotted as follows: Figure 3 The corresponding curves are shown.

[0036] Through analysis Figure 3 It can be seen that after initial friction and replacement of the mating spheres to disrupt the interface, the friction coefficient is high. At this time, the system resistance, CO, and Au release are all at high levels, indicating that the friction interface structure evolves rapidly, with gold particles migrating to the interface to replenish it, while the carbon film undergoes a tribochemical reaction. When gold replenishes the interface and forms a stable gold-rich transfer film, the friction coefficient decreases to a stable state, and the corresponding system resistance, CO, and Au release also decrease to low values, reflecting that the interface structure tends to stabilize. The phenomenon of the signal rising again after the stable interface is disrupted proves that the gold in the thin film can re-migrate to the newly formed friction interface to form a new lubricating film, thereby achieving the interface self-repair function.

[0037] Example 2: This embodiment uses the monitoring of the lubrication and self-healing behavior of copper / carbon nanocomposite thin films prepared by magnetron sputtering under extreme vacuum conditions as an example to illustrate the implementation process of the present invention in detail.

[0038] 1. System Connection according to Figure 1 The in-situ monitoring system is set up as shown. The mass spectrometer 2 is connected to the chamber 3 of the vacuum friction testing machine through the vacuum flange port. For the benchtop multimeter 1, two copper wires (with outer insulating ceramic sleeves) are used to connect its positive and negative terminals respectively, and the other ends of these two wires are introduced into the chamber 3 through the vacuum flange port, ready to be connected to the mating rod 11 and the friction clamping module respectively.

[0039] 2. Sample clamping The sample with the prepared copper / carbon nanocomposite thin film (substrate: 304 stainless steel, 1 mm thick) was mounted onto the sample clamping module of the vacuum tribometer. The mating balls were made of GCr15 bearing steel (6 mm diameter, approximately 20 nm roughness). The film surface and the mating ball surface were carefully cleaned using cotton balls soaked in anhydrous ethanol. The positive lead of the multimeter leading into the chamber was connected to the mating rod 11 via a metal screw, and the negative lead was connected to the clamping module. The clamping module was ensured to be in close contact with the back of the sample to form a complete electrical circuit: mating rod → mating ball → thin film → sample substrate → clamping module. Figure 2 As shown, the mating rod 11 adopts a segmented material design. The part that connects to the friction testing machine drive component (such as motor 7) must be insulated. A handheld multimeter is used to confirm that there is no electrical conductivity between the mating rod 11 and the friction assembly.

[0040] 3. Experimental Design and Parameter Setting To study the lubrication mechanism of thin films and their self-healing behavior after interface damage, the following scheme was designed: First, a steady-state friction was performed, then the dual spheres were removed and replaced with new dual spheres to disrupt the original friction interface. Subsequently, experiments were continued on the original wear marks, and the behavior was reflected by monitoring changes in resistance and mass spectrometry signals.

[0041] The friction test was set to reciprocating mode, with an amplitude of 5 mm, a frequency of 1 Hz, and a load of 1 N. The positions of the specimen and the mating rod were adjusted so that the mating ball was in contact with the specimen. Mechanical pump 8 and molecular pump 6 were started to evacuate chamber 3. When the vacuum level reached 2 × 10⁻⁶... -5 At mbar, turn on mass spectrometer 2 and set its acquisition interval to 7.942 seconds. Set benchtop multimeter 1 to resistance measurement mode and set its acquisition interval to 0.362 seconds. Continuously monitor until the intensity of background impurity signals such as H2O detected by the mass spectrometer decreases and stabilizes at the lowest level (approximately 20 minutes), then prepare to begin the triboelectric test.

[0042] 4. Data Acquisition, Processing and Analysis Once the background signal stabilizes, the friction program is initiated, and the friction coefficient, resistance value, and mass spectrometry signal (release intensity of Cu (mass-to-charge ratio 64)) are recorded simultaneously. After 450 seconds of friction, the friction reaches a stable state, at which point friction is paused and data acquisition is stopped. Subsequently, a new pair of balls is replaced, and the friction experiment is restarted at the original wear mark location, with the same parameters as in step 3. Once the friction coefficient decreases and stabilizes again (approximately 440 seconds later), all tests are stopped.

[0043] The collected data were processed: the release intensity of Cu per unit time was calculated. Data on the changes in friction coefficient, system resistance, CO release intensity, and Cu release intensity over time were integrated and plotted as follows: Figure 4 The corresponding curves are shown.

[0044] Through analysis Figure 4 It can be seen that after initial friction and replacement of the mating spheres to disrupt the interface, the friction coefficient is high. At this time, the system resistance, CO, and Cu release are all at high levels, indicating that the friction interface structure evolves drastically, with copper particles migrating to the interface to replenish it, while the carbon film undergoes a tribochemical reaction. When copper replenishes the interface and forms a stable copper-rich transfer film, the friction coefficient decreases to a stable state, and the corresponding system resistance, CO, and Cu release also decrease to low values, reflecting that the interface structure tends to stabilize. The phenomenon of the signal rising again after the stable interface is disrupted proves that copper in the film can re-migrate to the newly formed friction interface to form a new lubricating film, thereby achieving the interface self-repair function.

[0045] Comparative example: This comparative example uses the monitoring of the lubrication mechanism of copper / carbon nanocomposite thin films prepared by magnetron sputtering under extreme vacuum conditions to illustrate the limitations of wide-temperature-range online in-situ detection and analysis systems in the study of the lubrication and self-healing mechanisms of such metal / carbon nanocomposite thin films.

[0046] Turn on the Raman spectroscopy power supply, turn on the computer, turn on the spectroscopy host, and run the software self-test for 3 minutes; turn the key clockwise 90° to turn on the laser, adjust the height and position of the Raman lens, focus on the sample detection area, calibrate with the standard silicon wafer, set the laser wavelength to 514 nm, laser intensity to 50%, exposure time to 10 seconds, and the test range to 0-1000 cm⁻¹. -1 After calibration, set the experimental detection parameters as above, except that the test range is set to 0-2000 cm. -1 Next, turn on the power to the friction testing assembly pump, power on the friction testing machine, turn on the computer, and open the software; vent the vacuum and open the chamber, place the 304 sample block coated with a copper / carbon nanocomposite film into the sample holder, the dual sphere is a 6 mm diameter GCr15 steel ball, the sample height is 12 mm, the rotation radius is 17 mm, the test parameters are set to 1 N, 150 r / min, and the sampling frequency is 64 Hz; close the chamber door, open the vacuum software, and when the vacuum degree reaches 2 × 10⁻⁶... - 5 When the friction coefficient reaches mbar, begin the test as prompted. Stop the test after the friction coefficient stabilizes and friction has lasted for 20,000 seconds.

[0047] Since copper has no Raman activity, the Raman spectrum only shows the characteristic peaks of amorphous carbon. The collected Raman data of amorphous carbon was processed: the D and G peaks of amorphous carbon in the Raman spectrum were fitted separately, and the ratio of their areas was used as the determining factor. I D / I G Plotting the coefficient of friction over time yields the coefficient of friction and I D / I G Synchronous relationship curve of value changing over time ( Figure 5 ).

[0048] Through analysis Figure 5 It can be seen that the coefficient of friction is relatively high in the initial stage of friction, and I D / I G The value fluctuates wildly, indicating that the thin film interface structure evolves rapidly during this process; as friction continues, the friction coefficient becomes lower. I D / I G The value changes are relatively stable, reflecting that the friction interface structure has reached a stable state at this time.

[0049] Compared with the present invention, although in-situ Raman online analysis can also qualitatively reflect the evolution of the friction interface structure, it is difficult to further reflect the corresponding lubrication mechanism at different stages of the friction process. In addition, since copper has no Raman activity, it is also difficult to reveal the role of copper in the friction process by this method. The present invention has significant advantages in the in-depth analysis of the lubrication mechanism of such metal-doped hard coatings.

Claims

1. A method for achieving intelligent lubrication characteristics through in-situ monitoring of metal migration, characterized in that, A monitoring system comprising a vacuum friction testing machine, a mass spectrometer, and a benchtop multimeter is used, and the following steps are included: (1) System connection: The mass spectrometer is externally connected to the chamber of the vacuum friction testing machine via a flange port; The positive and negative leads of the benchtop multimeter are introduced into the chamber through flange ports, respectively; wherein, the positive lead is connected to the mating rod of the vacuum friction testing machine, and the end of the mating rod is equipped with a mating ball; the negative lead is connected to the sample clamping module of the vacuum friction testing machine. (2) Sample installation and circuit construction: The sample coated with a metal / carbon nanocomposite film is mounted on the sample clamping module, so that the sample clamping module, the sample, the dual ball and the dual rod together form a friction pair and an electrical monitoring circuit. Ensure that the mating rod is insulated from other moving components of the friction testing machine, and ensure that the specimen is in conductive contact with the specimen clamping module; (3) Parameter setting and vacuum preparation: Set the load, frequency, and amplitude parameters for the friction test; Set the benchtop multimeter to resistance measurement mode; Set the acquisition parameters of the mass spectrometer; Evacuate the chamber to the target vacuum level; (4) Synchronous in-situ monitoring and data acquisition: When the vacuum level in the chamber is stable and the background impurity signal of the mass spectrometer drops to its lowest level, the friction test procedure is started. Real-time acquisition of signals related to friction coefficient, friction pair resistance changes, and ion fragments released from the friction interface; (5) Lubrication behavior analysis: Establish curves showing the changes in friction coefficient, resistance value, and ion fragment release amount over time; By analyzing the correspondence and linkage among the three, the lubrication behavior and mechanism of the metal / carbon nanocomposite film during dynamic friction are revealed.

2. The method according to claim 1, characterized in that, The friction test was conducted in a reciprocating mode with a test frequency of less than 6 Hz.

3. The method according to claim 1, characterized in that, The mating rod adopts a segmented insulation design to ensure electrical insulation between it and the drive assembly of the vacuum friction testing machine.

4. The method according to claim 1, characterized in that, The benchtop multimeter has a resistance measurement range of 1 GΩ and a resolution of 10 μΩ.

5. The method according to claim 1, characterized in that, The mass spectrometer has a detection range of 1-200 u, a residence time of 1 ms-16 s / u, and a detection limit of 5 × 10⁻⁶. -19 mbar, vacuum level requirement below 10 -4 The vacuum level is in the mbar range, achieved by connecting a mechanical pump and a molecular pump in series.

6. The method according to claim 1, characterized in that, The substrate material of the sample is a conductive substrate, and the material of the dual spheres is a conductive material.

7. The method according to claim 6, characterized in that, The base material is 304 stainless steel, and the material of the mating ball is GCr15 bearing steel.

8. The method according to claim 1, characterized in that, The metal / carbon nanocomposite film is a gold / carbon nanocomposite film or a copper / carbon nanocomposite film, prepared by co-sputtering a metal target and a graphite target using magnetron sputtering technology.

9. The method according to claim 1, characterized in that, The ion fragment signal is the release intensity signal of gold ions with a mass-to-charge ratio of 197 or copper ions with a mass-to-charge ratio of 64.

10. The method according to claim 1, characterized in that, The lubrication behavior includes at least one of the following: migration of metal nanoparticles, formation and evolution of transfer films, and interface self-healing behavior.

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