Method for revealing 6H-SiC reciprocating friction cross-scale damage mechanism

Abstract

The invention discloses a method for revealing a 6H-SiC reciprocating friction cross-scale damage mechanism, which comprises the following steps: firstly, obtaining macroscopic friction wear behavior data of 6H-SiC through a reciprocating friction experiment under a series of loads; afterwards, the worn surface is analyzed in combination with a scanning electron microscope and an energy spectrum, a high-load worn section is observed by utilizing a focused ion beam and a high-resolution transmission electron microscope, and a cross-scale damage sequence of amorphization, nanocrystalline residue and microcrack propagation of the subsurface is directly revealed. Furthermore, the origin of key damage processes such as amorphization and dislocation activities is reproduced and explained from the atomic scale through molecular dynamics simulation. The method systematically reveals a damage evolution mechanism of 6H-SiC from an atomic scale to a microscale under reciprocating friction through a macroscopic experiment, microcosmic characterization and atomic simulation, and provides a systematic analysis means for deeply understanding tribological behaviors of the 6H-SiC and carrying out targeted performance research.

Description

Technical Field

[0001] This invention relates to the field of tribological properties research of advanced ceramic materials, specifically to a method for systematically revealing the damage evolution mechanism of 6H-SiC (hexagonal silicon carbide) ceramics under reciprocating friction conditions by comprehensively utilizing macroscopic experiments, microstructure characterization and molecular dynamics simulation, and providing guidance for wear performance regulation based on this mechanism understanding. Background Technology

[0002] Silicon carbide (SiC) is an ideal candidate material for critical structural components under extreme conditions due to its excellent hardness, wear resistance, high thermal conductivity, low coefficient of thermal expansion, and superior chemical stability. Among them, 6H-SiC, as one of the most stable hexagonal polymorphs, has shown great application potential in microelectromechanical systems (MEMS), aerospace bearings, advanced packaging, and high-temperature electronic devices. However, in these applications, components often endure high-frequency, high-load reciprocating sliding contact, leading to unavoidable friction and wear, which becomes a key limiting factor affecting device accuracy, stability, and service life.

[0003] Current research on the tribological behavior of SiC ceramics has made some progress. Numerous experimental studies have explored the effects of factors such as load, velocity, temperature, environmental medium, and mating materials on the friction coefficient and wear rate. For example, some studies have observed that increasing the load within a certain range may lead to a decrease in the friction coefficient and a non-monotonic change in the wear rate; the formation of oxide films at high temperatures may play a lubricating role; and tribochemical reactions may occur in aqueous environments. These studies are mainly based on the measurement of macroscopic tribological parameters and the morphological observation of the worn surface (e.g., using scanning electron microscopy, SEM). However, systematic and direct experimental observations and theoretical explanations are still lacking regarding the dynamic evolution of the subsurface microstructure of the material during wear, the mechanisms of damage initiation and early propagation, and especially the correlation and sequence between damage modes at different scales (atomic-nano-micron).

[0004] In recent years, molecular dynamics (MD) simulations have provided a powerful tool for studying the deformation and damage mechanisms of materials at the atomic / nanoscale. Existing simulations have revealed the phase transitions, amorphization, dislocation nucleation, and motion that may occur in SiC during nanoindentation and scratching. However, atomic-scale simulations are often disconnected from macroscopic experimental phenomena, failing to form an analytical framework that deeply integrates microscopic mechanisms, experimental observations, and macroscopic properties. This results in a lack of solid theoretical guidance for assessing and designing materials for wear resistance.

[0005] Therefore, there is an urgent need for a systematic research method that can connect macroscopic, microscopic, and atomic scales to deeply reveal the nature of frictional damage in 6H-SiC and provide a scientific basis for the proactive design of its properties.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] This invention aims to address the problem of unclear wear mechanisms, lack of systematic mechanistic explanations, and correlation analysis of 6H-SiC ceramics under high-load reciprocating friction conditions. Based on this, a comprehensive research method is provided to systematically reveal its cross-scale damage evolution sequence and its correlation with macroscopic tribological behavior. This method involves conducting reciprocating friction experiments on 6H-SiC under different normal loads (e.g., 5 N, 10 N, 30 N), and combining microstructural characterization and atomic-scale simulations to systematically study the law of wear rate variation with load, and to deeply analyze the damage characteristics of the material's subsurface under different wear states. Experimental results show that under specific moderate load conditions (e.g., 10 N), a continuous and dense SiO2 lubricating film can be formed on the material surface, at which point both the friction coefficient and wear rate reach a low level. Through high-resolution transmission electron microscopy observation of the wear cross-section, a cross-scale damage sequence with spatial order—"atomic-scale amorphization → nanocrystalline residue → microcrack propagation"—is revealed for the first time in the damaged region. Further molecular dynamics simulations reproduce and explain the above phenomena at the atomic interaction level. This method provides a complete research system combining experiments and simulations for a deep understanding of the damage evolution mechanism of 6H-SiC under reciprocating friction conditions and a systematic analysis of the intrinsic relationship between its macroscopic wear behavior and microstructure evolution.

[0008] 6H-SiC is a key structural ceramic material widely used in integrated circuit manufacturing, microelectromechanical systems (MEMS), and high-temperature bearings, possessing extremely high hardness, excellent thermal stability, and chemical inertness. However, its damage accumulation and failure mechanism under reciprocating sliding contact is complex. Traditional research struggles to establish a clear correlation between external loads, internal structural evolution, and the final wear outcome, leading to performance optimization primarily relying on empirical trial and error. More importantly, the 6H-SiC crystal structure exhibits anisotropy, with specific low stacking fault energy crystal planes (such as the SF(24) plane) readily becoming preferential pathways for dislocation slip and damage initiation under frictional stress. This characteristic makes understanding its cross-scale damage mechanism crucial for performance regulation.

[0009] This invention is achieved through the following technical solution: an analytical method for revealing the cross-scale damage mechanism of 6H-SiC reciprocating friction, comprising the following steps:

[0010] (1) Under three different normal load conditions of low, medium and high, the 6H-SiC ceramic sample was subjected to reciprocating friction test, the friction coefficient curve under each load was obtained and its wear rate was calculated.

[0011] (2) Using scanning electron microscope and energy dispersive spectroscopy, the morphology of the wear surface under each load was observed and the elemental distribution was analyzed to analyze the surface condition and wear mechanism.

[0012] (3) For wear specimens under high load conditions, longitudinal section samples are prepared using focused ion beam technology;

[0013] (4) The subsurface region of the cross-sectional sample is observed using a high-resolution transmission electron microscope. By analyzing the high-resolution lattice image, selected area electron diffraction spectrum and fast Fourier transform spectrum, the damage characteristics existing in the subsurface are identified and confirmed. These characteristics include: amorphized regions of crystal structure, nanoscale crystal residues located in amorphized regions or at interfaces, and microcracks that originate and extend from high defect density regions.

[0014] (5) Construct a 6H-SiC atomic model with the same orientation as the experimental crystal, use molecular dynamics to simulate the nano-scratching process at different indentation depths, analyze the deformation and damage mechanism at the atomic scale, and explain the phenomena observed in step (4).

[0015] (6) Based on the results of steps (1) to (5), analyze the correspondence between macroscopic friction and wear behavior, surface state, subsurface damage sequence and atomic scale mechanism under different loads.

[0016] Furthermore, the three different normal loads mentioned in step (1) are 5 N, 10 N and 30 N respectively; the reciprocating friction test has a stroke of 5 mm, a frequency of 2 Hz, a total duration of 30 minutes, and an experimental environment of room temperature of 23℃ and relative humidity of 50%.

[0017] Specifically, the mating component used in the complex friction experiment described in step (1) is a SiC ball with a diameter of 10 mm.

[0018] Furthermore, the 6H-SiC ceramic mentioned in step (1) is a pressureless sintered material with a bulk density of 3.14 g / cm³, a microhardness of 25.70 GPa, a flexural strength greater than 400 MPa, an elastic modulus of 415 GPa, and a thermal conductivity of 148 W·m. - ¹·K - ¹, fracture toughness is greater than 4.5 MPa·m¹ / ².

[0019] Furthermore, in step (2), the wear surface morphology under various loads was observed: under a low load of 5 N, the surface exhibited wear particles and spalling pits; under a medium load of 10 N, a relatively continuous and flat compacted layer was formed on the surface; under a high load of 30 N, the compacted layer exhibited a large-area cracking and spalling morphology, accompanied by a large number of microcracks; the main component of the compacted layer was oxygen-rich silicon oxide.

[0020] Furthermore, the subsurface region described in step (4) has a damage spatial sequence: in the high stress concentration region, an amorphous region with a completely disordered crystal structure first appears; within the amorphous region, there are nanocrystalline residues with a size of nanometer scale (2-10 nm) that still maintain a crystal structure; microcracks initiate from the high defect density region and extend along the grain boundary into the material.

[0021] Furthermore, the 6H-SiC atomic model described in step (5) has a size of 246.13 Å × 426.309 Å × 181.177 Å, a total of 1,843,200 atoms, and adopts the ABCACB stacking order, with the surface being the (0001) plane.

[0022] Furthermore, the molecular dynamics simulation described in step (5) uses LAMMPS software with a time step of 1 fs, employs the NPT system to relax for 100 ps at 293 K, and uses the Tersoff potential function to describe the interatomic interactions.

[0023] Specifically, the different indentation depths mentioned in step (5) include 10 Å, 20 Å and 30 Å. The simulation process is divided into three stages: indentation stage, reciprocating sliding stage and unloading stage. The sliding speed is 50 m / s, the scratch length is 150 Å, and the number of reciprocating cycles is 10. It also includes simulating a multi-cycle reciprocating sliding process. The multi-cycle simulation includes at least 5 cycles.

[0024] The construction of the 6H-SiC atomic model in step (5) is a highly targeted atomic-scale model construction and simulation specifically designed to explain experimental phenomena.

[0025] The model construction is directly experimentally benchmarked: the material used in the experiment is pressureless sintered 6H-SiC ceramic, and the constructed molecular dynamics model is a "6H-SiC atomic model consistent with the experimental crystal orientation." This means that the model construction does not adopt a general or arbitrary crystal orientation, but is directly based on the crystallographic characteristics of the actual experimental material, ensuring that the deformation mechanism at the atomic level in the simulation is comparable to the damage anisotropy observed in the experiment.

[0026] Specialization of potential function selection: The Tersoff potential function is used in the simulation to describe interatomic interactions. This potential function is recognized as a key tool for describing the structural and mechanical behavior of covalent materials such as silicon carbide (SiC). Its selection ensures the reliability of the simulation in terms of physical nature and can effectively reproduce atomic processes related to amorphization, such as bond angle distortion and bond breaking.

[0027] Systematic mapping between simulation parameters and experimental conditions: The simulation sets three different indentation depths of 10 Å, 20 Å, and 30 Å to systematically study the response under different contact stress states. This design directly corresponds to the three normal load gradients of 5 N, 10 N, and 30 N selected in the macroscopic experiment, aiming to map and explain the evolution of material behavior from elastic deformation and plastic initiation to severe damage under low to high loads at the atomic scale.

[0028] Through the targeted model constructed above, molecular dynamics simulation is no longer an independent theoretical calculation, but a key explanatory link connecting microscopic observational phenomena (amorphization, nanocrystals, microcracks) with atomic-scale physical origins (shear instability, dislocation motion). This directional simulation based on the characteristics of the experimental system is one of the core innovations of this method in achieving cross-scale connectivity from macroscopic behavior to atomic mechanisms.

[0029] This invention also provides an analytical system for revealing the cross-scale damage mechanism of 6H-SiC reciprocating friction, which can perform the above-mentioned analytical methods, including:

[0030] (1) Macroscopic tribological behavior testing unit, including reciprocating friction and wear testing machine, normal load loading module and data acquisition system, used to perform reciprocating friction experiment and record friction coefficient curve in real time;

[0031] (2) Surface wear condition characterization unit, including a scanning electron microscope and energy dispersive spectroscopy system, used to perform surface morphology observation and elemental surface distribution analysis of the worn surface;

[0032] (3) Subsurface damage preparation and observation unit, including a focused ion beam system and a high-resolution transmission electron microscope, used for cross-sectional sample preparation, subsurface observation and damage feature identification;

[0033] (4) Atomic-scale mechanism simulation unit, including a molecular dynamics simulation platform equipped with Tersoff potential function parameters and LAMMPS software, used to construct 6H-SiC atomic models and perform single and multi-cycle nano-scratching simulations at different indentation depths;

[0034] (5) Cross-scale correlation analysis platform, which integrates data processing and visualization software, is used to comprehensively analyze the output data of the macroscopic tribological behavior testing unit, surface wear state characterization unit, subsurface damage preparation and observation unit and atomic scale mechanism simulation unit.

[0035] This invention reveals a damage sequence of "amorphization → nanocrystalline residue → microcrack propagation," and a systematic analysis of the correlation between wear mechanisms and microscopic features under different loads. This provides important experimental evidence and mechanistic insights into the damage behavior of 6H-SiC during friction. Based on these findings, in engineering design, the working load of components can be set near the experimentally observed low wear rate load range. This allows for the utilization of the surface lubricating film formation phenomenon observed under these conditions, providing a potential reference based on experimental laws for optimizing the wear resistance of components. This method is not only applicable to tribological research on 6H-SiC, but its research approach and multi-scale analysis framework can also provide methodological guidance for the study of friction and wear mechanisms in other hard and brittle materials.

[0036] This invention also provides a specific application of the above method in material performance evaluation: for SiC materials used in MEMS devices, this method can be used to systematically study their wear behavior and damage characteristics under simulated working conditions, providing more comprehensive experimental data and mechanism analysis for evaluating their wear resistance and reliability in practical applications.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] 1. The method provided by this invention is the first to directly observe and verify the cross-scale sequence of subsurface damage of 6H-SiC under reciprocating friction, namely "amorphization → nanocrystal residue → microcrack propagation". Combined with atomic simulation, the origin of the related phenomena is explained from the mechanism level, providing important experimental and theoretical basis for a deeper understanding of its friction damage mechanism.

[0039] 2. The method provided by this invention systematically studies the influence of normal load on the wear behavior and subsurface damage characteristics of 6H-SiC, and analyzes the correlation between the dominant wear mechanism and microstructure evolution under different load ranges, providing systematic experimental research and analysis results for understanding the influence law of load in engineering.

[0040] 3. The method provided by this invention integrates macroscopic friction experiments, microstructure characterization, and atomic-scale simulation, forming a systematic and repeatable multi-scale research process. This research framework is not only applicable to 6H-SiC, but its methodological approach can also provide a reference for the study of friction and wear mechanisms in other material systems.

[0041] 4. Based on the research results and analytical methods obtained in this invention, a new perspective is provided for the application research and design evaluation of 6H-SiC in high-performance wear-resistant components. By systematically studying the behavior of the material under different loads, more sufficient experimental evidence and mechanistic understanding can be provided for the working condition design and performance evaluation of related components. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the linear reciprocating friction and wear testing device used in the embodiments of the present invention.

[0044] Figure 2 This is a schematic diagram of the atomic model of the three-dimensional molecular dynamics simulation of 6H-SiC established in the embodiments of the present invention.

[0045] Figure 3 This is a graph showing the evolution of the friction coefficient of 6H-SiC under different normal loads (5 N, 10 N, 30 N) over time, as measured in an embodiment of the present invention.

[0046] Figure 4 These are typical scanning electron microscope morphology comparison images of worn surfaces under different loads obtained in the embodiments of the present invention.

[0047] Figure 5 This is a schematic diagram of the observation results of the wear section under 30 N load by high-resolution transmission electron microscopy in an embodiment of the present invention, showing the subsurface damage sequence.

[0048] Figure 6 The graphs showing the changes in normal force, tangential force, and friction coefficient during a single scratching process at different indentation depths are obtained from molecular dynamics simulations in this embodiment of the invention.

[0049] Figure 7 This is a comparative schematic diagram of the microstructure of the system after different cycles at an indentation depth of 20 Å, obtained by molecular dynamics simulation in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0051] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures are not specifically described in order to avoid obscuring the invention.

[0052] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0054] Example 1

[0055] This invention provides a 6H-SiC research material and its experimental analysis method for revealing the multi-scale damage mechanism of reciprocating friction. The material is a pressureless sintered 6H-SiC ceramic with a bulk density of 3.14 g / cm³, a microhardness of 25.70 GPa, a flexural strength greater than 400 MPa, an elastic modulus of 415 GPa, and a thermal conductivity of 148 W·m. - ¹·K - ¹, fracture toughness greater than 4.5 MPa·m¹ / ². The test surface was polished to a mirror finish using a diamond suspension in stages, with a surface roughness Ra ≤ 0.02 μm. Before the experiment, all samples were cleaned sequentially in an ultrasonic cleaner with acetone, anhydrous ethanol, and deionized water for 15 minutes each, and then dried in a 60 ℃ oven for 2 hours.

[0056] An Rtec MFT-5000 multi-functional friction and wear testing machine, equipped with a linear reciprocating module, was used to conduct reciprocating friction experiments at room temperature (23℃) and relative humidity of 50%. The mating component was a 10 mm diameter SiC ball. Tests were conducted under three normal loads: 5 N, 10 N, and 30 N, with a stroke of 5 mm, a frequency of 2 Hz, and a total duration of 30 minutes. The friction coefficient was acquired and recorded in real time by a high-precision sensor. After the experiment, a three-dimensional surface profilometer was used to measure the wear traces, and the wear volume and wear rate were calculated.

[0057] like Figure 4 As shown, the wear surface of this material after reciprocating friction experiments under different normal loads (5 N, 10 N, 30 N) was characterized by scanning electron microscopy (SEM): under a low load of 5 N, the surface mainly showed wear particles and spalling pits; under a medium load of 10 N, a relatively continuous and flat compacted layer was formed on the surface; under a high load of 30 N, the compacted layer showed a large-area fracture and spalling morphology, accompanied by a large number of microcracks. Energy dispersive spectroscopy (EDS) surface scanning analysis confirmed that the compacted layers formed under 10 N and 30 N loads were mainly composed of oxygen-rich silicon oxide.

[0058] like Figure 5 As shown, longitudinal cross-sectional samples of wear specimens under a high load of 30 N were prepared using focused ion beam (FIB) and observed using high-resolution transmission electron microscopy (TEM). The results directly revealed the spatial sequence of damage existing on the subsurface: in high stress concentration regions (such as in front of the crack tip), amorphous regions with completely disordered crystal structures first appear; within these amorphous regions, nanocrystalline residues with nanoscale (2-10 nm) sizes that still maintain a crystalline structure are distributed; microcracks initiate from the above-mentioned high defect density regions and propagate along grain boundaries into the material interior. These observations constitute direct experimental evidence for the cross-scale damage evolution path.

[0059] Example 2

[0060] This invention also provides a system construction method for implementing the above-mentioned cross-scale damage mechanism research. This system integrates macroscopic experiments, microscopic characterization, and atomic simulation functions, specifically including:

[0061] (1) Macroscopic tribological testing unit: The Rtec MFT-5000 multi-functional friction and wear testing machine is used, equipped with a linear reciprocating module, such as... Figure 1 As shown, this unit can precisely control the normal load (5N, 10N, 30N), stroke (5 mm), and frequency (2 Hz), and records the friction coefficient curve in real time. After the experiment, a three-dimensional surface profilometer was used to accurately measure the wear volume and calculate the wear rate.

[0062] (2) Microstructure characterization unit: including scanning electron microscope and energy dispersive spectroscopy for analysis of wear surface morphology and elemental composition; focused ion beam system for preparing cross-sectional transmission electron microscope samples; high-resolution transmission electron microscope (accelerating voltage 300 kV, equipped with double spherical aberration corrector) for atomic-scale observation of subsurface crystal structure and defects. Damage characteristics such as amorphous regions, nanocrystalline residues, dislocations and stacking faults are identified through high-resolution lattice imaging, selected area electron diffraction and fast Fourier transform analysis.

[0063] (3) Atomic simulation calculation unit: A 6H-SiC atomic model with the same orientation as the experimental crystal was constructed using LAMMPS software. The model size was 246.13 Å × 426.309 Å × 181.177 Å, with a total of 1,843,200 atoms, stacked in an ABCACB order, with the upper surface being the (0001) plane. The Tersoff potential function was used to describe the interatomic interactions, and the potential function parameters were strictly set according to the literature. The simulation time step was 1 fs, and relaxation was performed for 100 ps under the NPT ensemble (T=293 K, P=0). The diamond indenter was modeled as a rigid sphere with a diameter of 120 Å, using a pure repulsive force model. The simulation process included three stages: indentation, reciprocating sliding, and unloading. The indentation depths were set to 10 Å, 20 Å, and 30 Å, respectively, the sliding speed was 50 m / s, the reciprocating stroke was 150 Å, and the total number of cycles was 10. Visual analysis was performed using OVITO software, and atomic configuration and defect evolution were analyzed using diamond structure recognition and dislocation extraction algorithms.

[0064] Example 3

[0065] This embodiment demonstrates how to use the system constructed in Example 2 to conduct a complete systematic analysis of the tribological behavior and damage mechanism of 6H-SiC, achieving multi-scale analysis including macroscopic experiments, microscopic characterization, and atomic simulation.

[0066] (1) Macroscopic behavior acquisition and correlation: This is achieved through macroscopic tribological testing units, such as... Figure 3 The friction coefficient curves shown yielded average friction coefficients of 0.698 (5 N), 0.587 (10 N), and 0.382 (30 N), respectively. The wear rate was lowest at 10 N, at 1.85 × 10⁻⁶. -5 mm³ / N·m. Combined with surface analysis results from SEM / EDS ( Figure 4 The correlation between macroscopic behavior and surface mechanism was established: 5 N corresponds to abrasive wear characterized by wear particles and spalling pits; 10 N corresponds to oxidation-adhesion wear that forms a continuous SiO2 lubricating film; and 30 N corresponds to oxidation-abrasive coupled wear that is accompanied by lubricating film rupture and a large number of microcracks.

[0067] (2) Direct verification and mechanism correlation of subsurface damage sequence: For a 30 N high-load sample, the cross-section was prepared and observed using the FIB-TEM process. Figure 5 This directly yielded evidence of a damage sequence of "amorphization → nanocrystalline residue → microcrack propagation." High-resolution TEM images showed that the crack tip region was completely amorphous, with high-density stacking faults in front of it. This step directly correlated the high wear rate state with specific, severe subsurface multiscale damage, indicating that material removal follows an evolutionary path from atomic disorder to microcracks.

[0068] (3) Atomic-scale mechanism simulation and interpretation: Molecular dynamics simulation was performed using atomic simulation computing units to reproduce the scratching process at different indentation depths. Figure 6 Simulation results show that under shallow compressive strength (10 Å), the material undergoes predominantly elastic deformation with an extremely low friction coefficient (~0.02) and no permanent damage. Under deep compressive strength (20-30 Å), plastic deformation dominates, leading to subsurface amorphization, dislocation nucleation and slip (especially partial dislocations slipping along the low stacking fault energy SF(24) plane), and the formation of nanocrystalline clusters encapsulated in the amorphous region. These atomic processes directly explain the origin of the amorphous / nanocrystalline composite structure, dislocation entanglement, and microcracks observed by TEM.

[0069] (4) Cyclic cumulative damage process and steady state analysis: Further multi-cycle reciprocating scratch simulation was conducted (taking a pressure depth of 20 Å as an example). Figure 7 By comparing parameters such as atomic configuration, dislocation structure, and number of amorphous atoms after different cycles, the cumulative effect of damage was analyzed. Simulations revealed that the system undergoes drastic changes in the first approximately five cycles, after which the friction coefficient, normal / tangential force, and microstructure parameters tend to reach dynamic equilibrium. This provides a reasonable atomic-scale explanation for the "run-in effect" in macroscopic tribology and the subsequent formation mechanism of a stable wear state, revealing the microscopic processes of damage saturation and material response softening.

[0070] Example 4

[0071] This embodiment, based on the multi-scale damage mechanism of 6H-SiC under reciprocating friction disclosed in the foregoing embodiments, provides a framework for evaluating and optimizing 6H-SiC components using this mechanism in engineering design. This framework directly stems from the experimental laws and mechanistic understanding revealed by the method of this invention, aiming to transform multi-scale research results into useful guidance for the design of 6H-SiC components.

[0072] The working load range was optimized based on the correlation between load and wear mechanisms. Experimental results show that under a normal load of 10 N, 6H-SiC exhibits the lowest wear rate due to the formation of a continuous and dense SiO2 lubricating film. Therefore, in component design, the contact stress in actual working conditions can be equivalently represented by the normal load in this study through contact mechanics analysis. If the equivalent load falls within the range of 10 N, it indicates that this working condition is conducive to achieving low-wear operation by utilizing the SiO2 lubricating film generated in situ during friction. This assessment provides direct experimental basis for setting the load parameters of SiC components.

[0073] Crystal orientation was assessed based on the anisotropy of crystals during damage evolution. Molecular dynamics simulations and TEM observations jointly showed that dislocation slip and damage propagation preferentially occur along the SF(24) plane with low stacking fault energy. This finding suggests that the relationship between crystal orientation and the main stress direction should be evaluated when designing or fabricating 6H-SiC components. If such weak planes can be made to avoid the direction of maximum shear stress, it may be possible to structurally suppress the preferential initiation and propagation of damage. This assessment stems from the direct revelation of the damage anisotropy mechanism in this study, providing a theoretical basis for optimizing component performance using crystal orientation.

[0074] Running-in phase management is based on the cyclic stabilization phenomenon. Atomic simulations show that the system enters a stable wear state after approximately five cycles, with parameters such as the friction coefficient and the number of amorphous atoms tending towards dynamic equilibrium. This finding provides a microscopic explanation for understanding the initial operating phase of the component. In actual operation, this pattern can be used to understand the initial friction coefficient variation process, distinguishing the drastic initial running-in phase from the subsequent stable operating phase. This provides a theoretical background for component operation and maintenance strategies and helps in developing reasonable running-in period management plans.

[0075] The above design considerations are all directly derived from the cross-scale damage mechanisms revealed by the method of this invention, including the load-wear mechanism correspondence, the crystallographic origin of the damage sequence, and the cyclic stabilization phenomenon. This embodiment demonstrates how to transform these research findings into qualitative evaluation approaches for engineering design, thereby shifting traditional empirical design towards a more theoretically guided direction and improving the reliability and life prediction accuracy of 6H-SiC component design.

Claims

1. An analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction, characterized in that, Includes the following steps: (1) Under low, medium and high normal load conditions, reciprocating friction test was carried out on 6H-SiC ceramic samples to obtain the friction coefficient curves under each load and calculate its wear rate. (2) Using scanning electron microscope and energy dispersive spectroscopy, the morphology of the wear surface under each load was observed and the elemental distribution was analyzed to analyze the surface condition and wear mechanism. (3) For wear specimens under high load conditions, longitudinal section samples are prepared using focused ion beam technology; (4) The subsurface region of the cross-sectional sample is observed using a high-resolution transmission electron microscope. By analyzing the high-resolution lattice image, selected area electron diffraction spectrum and fast Fourier transform spectrum, the damage characteristics existing in the subsurface are identified and confirmed. These characteristics include: amorphized regions of crystal structure, nanoscale crystal residues located in amorphized regions or at interfaces, and microcracks that originate and extend from high defect density regions. (5) Construct a 6H-SiC atomic model with the same orientation as the experimental crystal, use molecular dynamics to simulate the nano-scratching process at different indentation depths, analyze the deformation and damage mechanism at the atomic scale, and explain the phenomena observed in step (4). (6) Based on the results of steps (1) to (5), analyze the correspondence between macroscopic friction and wear behavior, surface state, subsurface damage sequence and atomic scale mechanism under different loads.

2. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1, characterized in that: The three different normal loads mentioned in step (1) are 5 N, 10 N and 30 N respectively; the reciprocating friction test has a stroke of 5 mm, a frequency of 2 Hz and a total duration of 30 minutes, and the experimental environment is room temperature of 23℃ and relative humidity of 50%.

3. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 2, characterized in that: The mating component used in the complex friction experiment described in step (1) is a SiC ball with a diameter of 10 mm.

4. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1, characterized in that: The 6H-SiC ceramic mentioned in step (1) is a pressureless sintered material with a bulk density of 3.14 g / cm³, a microhardness of 25.70 GPa, a flexural strength greater than 400 MPa, an elastic modulus of 415 GPa, and a thermal conductivity of 148 W·m. - ¹·K - ¹, fracture toughness is greater than 4.5 MPa·m¹ / ².

5. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 2, characterized in that: In step (2), the wear surface morphology under various loads was observed: under a low load of 5 N, the surface showed wear particles and spalling pits; under a medium load of 10 N, a relatively continuous and flat compacted layer was formed on the surface; under a high load of 30 N, the compacted layer showed a large area of ​​cracking and spalling, accompanied by a large number of microcracks; the main component of the compacted layer was oxygen-rich silicon oxide.

6. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1, characterized in that: In step (4), the subsurface region has a damage spatial sequence: in the high stress concentration region, an amorphous region with a completely disordered crystal structure first appears; inside the amorphous region, there are nanocrystalline residues with a size of nanometer (2-10 nm) that still maintain the crystal structure; microcracks initiate from the high defect density region and extend along the grain boundary into the material.

7. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1, characterized in that: The 6H-SiC atomic model described in step (5) has a size of 246.13 Å × 426.309 Å × 181.177 Å, a total of 1,843,200 atoms, and adopts the ABCACB stacking order, with the surface being the (0001) plane.

8. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1 or 7, characterized in that: The molecular dynamics simulation described in step (5) uses LAMMPS software with a time step of 1 fs. The NPT system is used to relax for 100 ps at 293 K, and the Tersoff potential function is used to describe the interatomic interactions.

9. The analytical method for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction according to claim 1, characterized in that: The different indentation depths mentioned in step (5) include 10 Å, 20 Å and 30 Å. The simulation process is divided into three stages: indentation stage, reciprocating sliding stage and unloading stage. The sliding speed is 50 m / s, the scratch length is 150 Å, and the number of reciprocating cycles is 10. It also includes simulating a multi-cycle reciprocating sliding process. The multi-cycle simulation includes at least 5 cycles.

10. An analytical system for revealing the multi-scale damage mechanism of 6H-SiC reciprocating friction, characterized in that: The analytical method described in any one of claims 1-9 can be performed, comprising: (1) Macroscopic tribological behavior testing unit, including reciprocating friction and wear testing machine, normal load loading module and data acquisition system, used to perform reciprocating friction experiment and record friction coefficient curve in real time; (2) Surface wear condition characterization unit, including a scanning electron microscope and energy dispersive spectroscopy system, used to perform surface morphology observation and elemental surface distribution analysis of the worn surface; (3) Subsurface damage preparation and observation unit, including a focused ion beam system and a high-resolution transmission electron microscope, used for cross-sectional sample preparation, subsurface observation and damage feature identification; (4) Atomic-scale mechanism simulation unit, including a molecular dynamics simulation platform equipped with Tersoff potential function parameters and LAMMPS software, used to construct 6H-SiC atomic models and perform single and multi-cycle nano-scratching simulations at different indentation depths; (5) Cross-scale correlation analysis platform, which integrates data processing and visualization software, is used to comprehensively analyze the output data of the macroscopic tribological behavior testing unit, surface wear state characterization unit, subsurface damage preparation and observation unit and atomic scale mechanism simulation unit.

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