Li4SiO4 is a promising solid-state tritium breeder material due to its high lithium density and low tritium retention. Under irradiation, lithium vacancies are the predominant defects formed, influencing tritium release behavior. This study systematically investigates tritium adsorption and diffusion in different lithium vacancy configurations within Li4SiO4 using first-principles calculations. The investigation covers three stages: first, adsorption and migration characteristics within vacancies; second, adsorption sites and migration behaviors after escape; finally, diffusion coefficients for both processes. The results show maximum adsorption energies of −1.597 eV (within vacancies) and −1.638 eV (after escape). The minimum migration energy barriers within the three vacancy configurations are 0.231 eV, 0.129 eV, and 0.091 eV, with corresponding optimal escape barriers of 0.236 eV, 0.373 eV, and 0.766 eV. The optimal migration pathways were identified as TⅣ→TⅢ→O37, PⅤ→PⅢ→PⅡ→O19, and OⅤ→OⅣ→O30. At 900 K, diffusion coefficients are 1.63 × 10−7 m2/s (within vacancies) and 2.96 × 10−8 m2/s (escape), with the former being approximately one order of magnitude higher, indicating greater mobility within the vacancies. The results provide an atomistic understanding of the individual stages of tritium migration and can indirectly inform subsequent breeder material design and fabrication.

The reflood cooling process, as a heat transfer process for cooling at high temperatures, evolves from single-phase forced convection heat transfer to two-phase heat transfer, successively experiencing the stages of dispersed flow, inverse annular flow, and transition boiling, representing typical post-CHF heat transfer behavior. Although the single-phase heat transfer and film boiling stages during the reflooding process can be assessed using existing quasi-steady-state post-CHF prediction methods, there is a lack of predictive pathways for the rapidly increasing heat transfer coefficients and the transition timing between the various stages of reflooding during the transition boiling phase. In this study, the relationship between temporal liquid fraction and heat transfer coefficient was obtained through reflooding visualization experiments. After correlation analysis, the influence of temporal liquid fraction on heat transfer behavior was excluded, allowing the assumption of a constant heat transfer coefficient during film boiling. Further considering heat conduction as the dominant mechanism in regions with rapidly increasing heat transfer coefficients, a simplified mechanistic model was developed and validated. Construct quasi-steady-state prediction relationships for radiative heat transfer, convective heat transfer, and the propagation velocity of the cooling front, with prediction deviations within 10%. Additionally, perform droplet entrainment theoretical analyses and statistical analyses respectively for the transition timing between the two heat transfer stages, and provide predictive methods for these transition timings. Finally, a heat transfer evolution prediction model for the entire reflood cooling process in a rectangular narrow channel was established and compared with experimental data.

An accurate understanding of the breakup mechanisms of liquid films and reliable prediction of the post-breakup coverage fraction are crucial for the thermal design and safety analysis of falling-film cooling systems. Existing experimental and modeling studies focusing on film breakup have predominantly based on isothermal conditions, which differ from practical heat transfer scenarios. In this work, falling film experiments were conducted on a 90 mm horizontal heated copper tube within the mass flow rate per unit length of 0.017-0.099 kg/m & sdot;s, and an infrared-based method was employed to accurately measure the liquid coverage fraction. Quantitative data were obtained to elucidate the breakup process and identify the key factors influencing liquid coverage. A model for liquid coverage fraction prediction was developed, which characterizes the film breakup process and systematically incorporates the effects of Marangoni effect and hydrodynamic boundary layer development. Validation against in-house experimental data and independent results from the literature confirms that the model is applicable to both tubular and planar falling-film configurations, and can therefore serve as a basis for predicting post-breakup heat transfer behavior. This work provides a practical tool for coverage prediction and advances the understanding of heated film breakup.

Helical coiled tubes feature a uniform inclination and constant curvature, in which the boiling two-phase flow is influenced by both mechanical forces and secondary flow structures, thereby affecting the characteristics and mechanisms of flow instability. This study experimentally investigates flow instability in parallel helical coils under uniform constant wall temperature conditions, focusing on the effects of inlet throttling coefficient, inlet subcooling, inlet mass flow rate, and system pressure. The underlying mechanisms are elucidated through theoretical analysis, highlighting the roles of mechanical and secondary flow effects. Results indicate that increasing the inlet throttling coefficient suppresses phase asynchrony in flow oscillations among parallel coils, thereby mitigating flow instability. Increasing inlet subcooling first reduces and then amplifies the oscillation amplitude, whereas higher system pressure enhances stability. Pressure drop analysis reveals that the subcooled section contributes less than 5% of the total pressure drop, thus having a limited effect on system stabilization. In contrast, variations in the two-phase pressure drop fraction, governed by mechanical and secondary flow effects, are the primary factors influencing system stability.

The local deformation of plate fuel assembly due to neutron irradiation will lead to the deterioration of heat transfer in the flow channel. Studying the characteristics of annular flow films in narrow rectangular channels under localized deformation provides a foundation for understanding the heat and mass transfer and the hydrodynamic characteristics of the locally deformed narrow flow channel. In this study, the annular flow liquid film characterization experiments were conducted in a narrow rectangular channel under three conditions: no local deformation, ellipsoidal deformation, and pillow-shaped deformation. Various parameters of the annular flow liquid films, including liquid film thickness, disturbance wave height, and disturbance wave wavelength, were obtained using a high-speed camera acquisition system and advanced image processing techniques. The effects of flow conditions and local deformation on the liquid film parameters of each annular flow were analyzed. As the radial size of the local deformation increases relative to the liquid film thickness, the viscous bottom layer of the liquid film disintegrates, resulting in a reduction of the total liquid film thickness. When the gas-phase velocity is low, the local deformation exerts a greater shear force on the disturbance wave, prolonging the action time and increasing the likelihood of wave disintegration. Under conditions of no channel deformation, the disturbance wave wavelength is negatively correlated with the gas-phase velocity; conversely, under localized channel deformation, the wavelength is positively correlated with the gas-phase velocity. Thus, the effect of localized deformation on wavelength is bidirectional. Local deformation impact factor functions for liquid film thickness, disturbance wave height, and disturbance wave wavelength have been derived, with the error of these impact factor functions maintained within +/- 30 %.

The supercritical carbon dioxide (SCO2) Brayton cycle offers a compact configuration and high thermal efficiency, making it a promising power conversion system for micro modular reactors (MMR). However, the strong coupling between the reactor and the Brayton loop under accident conditions introduces complex transient behaviors, and the local thermal response of PCHE during such events remains insufficiently understood. To address these issues, this study develops a thermal-hydraulic analysis code for a SCO2 Brayton cycle MMR system using the Modelica language. Validation results confirm that the code exhibits satisfactory reliability under both steady-state and transient conditions. Based on the validated code, two representative accident scenarios, external load loss (10%–40%) and reactivity insertion (20–150 pcm) are investigated. Results show that both accidents lead to increases in system pressure and rotor speed, as well as a decline in cycle efficiency. The inherent reactivity feedback of the core effectively suppresses excessive power excursions, maintaining fuel and cladding temperatures within allowable safety margins. Notably, pronounced thermal transients occur within the PCHE during both accidents, characterized by stepwise increases in structural heat storage (exceeding 30% in the precooler) and significant local wall temperature differences across the transient. This study provides a reference for the design and accident mitigation of SCO2 Brayton cycle reactor systems.

Flow-induced vibration (FIV) of cylinders provides a promising pathway for ambient wind energy harvesting, yet its practical application is constrained by a narrow lock-in region and limited operational bandwidth. This study proposes a three-cylinder piezoelectric energy harvester (TC-PEH) that leverages the coupled dynamics of vortexinduced vibration (VIV) and wake-induced galloping (WIG) to overcome these limitations. Wind tunnel experiments were conducted over wind speeds from 0.5 to 10 m/s to systematically examine the influence of both uniform and non-uniform spacing ratio configurations. The findings demonstrate that spacing ratio L/D plays a decisive role in governing the FIV regime, at L/D = 1.3, the system exhibits strongly coupled, upstreamdominated WIG, while larger spacings lead to decoupled VIV and WIG behavior. According to the proposed regime, the optimal uniform arrangement (L/D = 1.3) delivers a 15-fold increase in average output power and a 4.1-fold rise in output voltage relative to a single-cylinder baseline, with consistently stable voltage across most of the operating range. Furthermore, a strategically engineered non-uniform spacing (L1/D = 1.5, L2/D = 1.3) enhances maximum output power by 25% and induces downstream synergy, achieving peak output voltages up to 40 V. These results confirm that spacing optimization enables robust VIV-WIG coupling in multi-cylinder arrays. This work establishes a high-efficiency, wide-bandwidth design framework for FIV-based energy harvesters serving micro-electro-mechanical systems (MEMS) applications.

This paper conducts a numerical investigation of flow characteristics and vibrations in a 7-pin wire-wrapped fuel rods bundle subjected to lead-bismuth eutectic (LBE) axial flow. In this paper, the flow characteristics of 7-pin rods bundle with two different wire-wrapped diameters is analyzed firstly. Then, the effect of the constraint of the adjacent rods to the center rods on the vibration response of the bundle is analyzed. Meanwhile, the effect of constraint conditions at the upper end of the bundle on the vibration behavior is discussed. It is indicated that increasing the wire-wrapped diameter changing from 1.9 mm to 2.0 mm impacts flow characteristics insignificantly. The fluid force on the central rod surface exceeds that on adjacent rods in the bundle configuration. Notably, when introducing normal contact between the wire of the center rod and the adjacent rods, the vibration displacement at the central rod's midpoint decreases by 81 %, while the dominant frequency increases from 15 Hz to 40 Hz. As the upper-end constraint condition changes from simply support, Y-direction support to no support, the vibration displacement of the center rod changes significantly along the axial direction. When the lower end is fixed support and the upper end is no support, the vibration displacement of the upper end increases along the axial direction, and the root mean square at the upper end (Z = 1500 mm) reaches 68.70 mu m. These findings provide a theoretical foundation for the design optimization of wire-wrapped rod bundles in lead-bismuth-cooled fast reactors.

The reflooding quenching process in rectangular channels is a critical thermal-hydraulic phenomenon for reactor safety during Loss-of-Coolant Accidents (LOCAs). While data-driven models offer high efficiency, their application is often hindered by a lack of physical consistency and mechanistic interpretability. This study systematically evaluates four machine learning architectures-RF, LSTM, TCN, and Transformer-using a 200-point gradient-based adaptive sampling strategy to reconstruct transient quenching curves. The proposed framework integrates physical consistency validation based on a gradient threshold, and SHAP-based explainability. Results demonstrate that the RF model achieves superior performance with an R2 of 0.9532 and an MAE of 21.89 degrees C. The minimum film boiling temperature was predicted with an RMSE of 24 degrees C. SHAP analysis identified initial wall temperature and inlet subcooling as the primary physical drivers, while high-order lag features in the RF model highlighted the essential role of long-term thermal memory. This comprehensive approach enhances engineering trust and provides a robust, physically-validated tool for reactor safety analysis.

Surface roughness represents a fundamental parameter governing vapor-liquid interfacial behaviors and critical heat flux (CHF) in boiling system. Separated effect of roughness on CHF in subcooled flow boiling is studied in this work, employing copper surface with controlled averaged roughness (Ra) ranging from 0.141 mu m to 2.135 mu m. The surface wettability is moderately influenced and surface negligible wickability is maintained. The results demonstrate a consistent non-monotonic relationship between roughness and CHF across the tested range of mass fluxes (100 to 400 kg/m(2)s). As Ra increases, the CHF initially rises and peaks at Ra=0.699 mu m, exhibiting a similar to 30% enhancement compared to the CHF at the smoothest surface (Ra=0.141 mu m). Then, the CHF stabilizes or even experiences a slight decline with further increases in roughness. The impact trend is attributed to the limitedly increased nucleation site density, restricted microlayer evaporation, and increased liquid rewetting friction under high Ra. In addition, the thermal parameters effect, including mass flux, subcooling, and pressure, is studied, and the increasing trend is explained based on the visualization results of vapor-liquid dynamics. Building upon these experimental insights, a prediction model for CHF is established considering the roughness effect and thermal parameter effect, with a good agreement of +/- 15% errors compared to experimental data. The findings provide insights into surface fabrication on boiling heat transfer enhancement and safety design in boiling systems.

Similar to the post-CHF heat transfer stage, the precursory cooling stage after LOCA shares similarities in heat transfer mechanisms, as both involve the film boiling heat transfer process. In contrast to prior investigations on precursory cooling, this pioneering study explores the evolution of precursory cooling heat transfer under varying uncovered proportions (residual water heights) and thermo-hydraulic parameters during the partially exposed conditions of the reflooding process, specifically focusing on scenarios with a residual water level. A key finding is that the residual water height at the base of the high-temperature channel can modify the downstream precursory cooling influence mechanism. Through comparative analysis, this article found that the traditional post-CHF heat transfer correlation is difficult to characterize the temporal changes of reflood cooling and the influence of residual water height. Grounded in the precursory cooling heat transfer characteristics under partially exposed states, this article constructs a heat transfer relationship for the reflooding process of narrow rectangular channels under such conditions. It successfully forecasts the precursory cooling heat transfer behavior across different residual water heights, with over 95 % of the predicted data aligning with experimental data within an error margin of +/- 25 %.

The thermo-hydraulic performance of printed circuit heat exchangers (PCHEs) plays a critical role in ensuring power supply and supporting the development of specialized equipment in mobile microreactors. In this study, helium and air were selected as working fluids to perform 75 numerical simulation cases of PCHEs with semicircular, rectangular, and triangular channels. The study investigated the influence of inlet parameters on the thermo-hydraulic performance of PCHEs with different channel geometries. Results indicated that the semicircular channel PCHE exhibited a uniform gradient of heat transfer along the flow direction, with the heat transfer rate increasing consistently. Heat transfer rate of the semicircular channel is enhanced by 4.46% and 11.16% compared with that of the rectangular and triangular channels, respectively, across all operating conditions. Moreover, it achieves the highest heat transfer rate of 31.53 kW and a maximum overall heat transfer coefficient of 4500.9 W/m2 & sdot;K. The flow and resistance characteristics of different channel geometries were also revealed: rectangular channels generated corner-vortex dissipation, intensifying kinetic energy loss, while triangular channels exhibited stagnant zones at sharp corners, leading to poor flow stability. Consequently, the semicircular-channel design exhibited the lowest flow resistance and pressure drop. Furthermore, Nusselt number and friction factor correlations applicable to laminar flow conditions were proposed, with a maximum deviation of 13.6% between predicted and simulated values. Overall, the semicircular-channel PCHE demonstrated superior integrated performance. This study compares three PCHE channel geometries with equal heat-transfer areas. The semicircular channel shows the highest thermal performance, whereas the triangular channel exhibits the largest pressure drop. These findings provide a valuable reference for the mechanism exploration and performance assessment of helium-air PCHEs in mobile microreactors.

Flow-induced vibration in pressurized water reactors can trigger fretting between foreign objects and cladding. However, the wear behavior of Zr-4 cladding under water-lubricated line contact remains insufficiently quantified. This work developed a custom fretting rig, which was used to investigate the fretting wear characteristics of Zr-4 alloy cladding by varying the cycle number and displacement amplitude. The corresponding wear volume and maximum wear depth were measured using white-light interferometry, and scar morphology, debris evolution, and elemental transfer/oxidation were characterized by SEM/EDS. Results showed that a water film and compacted third-body layer mitigated direct metal contact and simultaneously, debris erosion produced pits were observed during the Zr-4 cladding wear, in which debris oxidation mainly occurred and Fe transfer from the counter-body was most pronounced. With the increasing of cycles, wear depth and volume increased and the process was divided into three stages: Rapid Rise (n <= 1.2 & times; 10(6) th), Running-in (1.2 & times; 10(6) th < n <= 2.0 & times; 10(6) th), and Stable Wear (n > 2.0 & times; 10(6) th), with a maximum values occurring at 3.2 & times; 10(6) cycles (d approximate to 4.0 mu m, V approximate to 6.1 & times; 10(-3) mm(3)). Increasing displacement amplitude (D) also raised wear characteristics, defining Low Wear (D <= 20 mu m), Accelerated (20 < D <= 60 mu m), and Stable (D > 60 mu m) regions. At a displacement of approximately 60 mu m, intensified cracking and debris generation were observed. The energy-normalized wear rate and wear-depth rate both peaked during the initial stage and in the high-amplitude accelerated wear regime, then gradually declined as the interface stabilized. Specifically, when the number of cycles was approximately 1.2 & times; 10(6), these values reached about 4.40 & times; 10(3) mu m(3)/Nm and 2.92 & times; 10(-3) mu m/Nm, respectively; while in the displacement amplitude acceleration zone, their peaks were around 2.91 & times; 10(3) mu m(3)/Nm and 1.92 & times; 10(-3) mu m/Nm. Overall, center-scar damage was dominated by abrasive/adhesive wear, while the edges were dominated by abrasive wear, and oxidative wear persisted throughout.

This study aims to reveal the atomic-scale mechanisms of bubble nucleation and heat transfer characteristics in oxidized surface pool boiling through molecular dynamics simulations. A zirconium alloy surface model with varying degrees of oxidation coverage (phi) was constructed, and the boiling process was simulated. The activation energy equation for heterogeneous bubble nucleation was derived in conjunction with thermodynamic theories. For the first time, a systematic investigation into the influence of partially oxidized surfaces (0% <= phi <= 100%) on nucleation was conducted, filling the gap left by homogeneous surface simulations. The results reveal that the bubble nucleation waiting time significantly increases with phi, extending from 1013.07 at phi = 0% to 6075.16 at phi = 100%, indicating that oxidation inhibits nucleation. The heat flux initially decreases and then increases with phi, reaching a minimum at phi = 25%. The magnitude of the solid-liquid interaction potential energy determines whether nucleation occurs, while its distribution controls the nucleation location. Furthermore, the critical activation energy increases with phi, providing a thermodynamic explanation for the increased nucleation difficulty. This work provides an atomic-scale theoretical foundation for optimizing heat dissipation and ensuring the safe design of zirconium alloy cladding in nuclear reactors.

Lithium orthosilicate (Li4SiO4) is a promising breeder material with its high lithium density and low tritium retention for fusion reactor blanket. After neutron irradiation, Li4SiO4 not only produces tritium but also forms lithium vacancy defects, which may significantly influence the release and collection of tritium. Therefore, in this paper, the adsorption characteristics of tritium in different lithium vacancy defects of Li4SiO4 were systematically studied based on first principles to understand the influence mechanism of lithium vacancies on tritium. Tritium breeder materials are exposed to a flowing mixed-gas atmosphere of helium and hydrogen. In this typical oxygenpoor (O-poor) operational environment, the formation energies were investigated. For comparison, oxygen-rich (O-rich) conditions were also considered. The formation energies, possible adsorption sites and electronic properties of defects were analyzed by constructing lithium vacancy models and tritium adsorption models. It was found that the formation energies of lithium vacancies (VLi) under O-rich conditions were 1.21-2.16 eV compared with the lithium vacancy-tritium defect complexes (VLi-T) of 0.52-1.12 eV, which indicates that VLi-T is easier to form than VLi under the same conditions. Additionally, the adsorption energies of tritium in VLi range from -7.021 to -5.581 eV, showing that VLi has a strong tritium capture ability. Subsequently, by analyzing multiple possible adsorption sites, it was determined that the octahedral VLi-T configuration, with an average formation energy of 1.24 eV, is more difficult to form. Finally, electronic property analysis suggested that tritium interacts with the 2p orbital of oxygen to form VLi-T. The study presented in this paper will provide practical guidance for optimizing tritium breeder materials and designing tritium blankets in the future.

Among the various technologies for the production of medical isotopes, solution reactors offer several advantages, including safety, high efficiency, and cost-effectiveness. During the operation of solution reactors, gas-liquid two-phase flow are formed due to the presence of radiolytic bubbles and the density difference between the phases. Investigating the heat transfer characteristics of the gas-liquid flow in solution reactors is crucial for their design and operation. To investigate the influence of the size distribution of radiolytic bubbles on the two-phase flow and heat transfer characteristics in a Medical Isotope Production Reactor (MIPR), numerical simulations based on the Eulerian multiphase model and the population balance model (PBM) were performed. The flow and temperature fields in the reactor were compared and analyzed for bubble size distributions of 0.35-2 mm and 0.001-2 mm. It was observed that the direction of gas-phase movement in the 0.001-2 mm bubble swarm is significantly affected by the liquid phase. Microbubbles encountered greater difficulty in escaping the liquid surface. This leads to higher maximum solution temperature and a larger average gas-phase volume fraction within the reactor. Variations in bubble diameter directly induce changes in the two-phase flow field, thus influencing the final bubble concentration and gas-phase distribution. When microbubbles are present, strong natural convection occurs at both the bottom and upper middle of the solution, with a region of weak convection between these two areas. This study can serve as a reference for future thermal-hydraulic analyses of the solution reactor.

Nanoscale interfacial dynamics in flow boiling critically impact nuclear reactor safety, while the nucleation mechanism of flow boiling bubbles lacks of clear understanding. This paper focuses on this goal, and the nucleation and flow boiling bubble behavior on zirconium metal substrates are investigated through molecular dynamics simulations. The study identifies three bubble modes: growth, collapse, and metastable nucleation. Bubble nucleation and growth are governed by competition between the kinetic and potential energy of water molecules in the liquid layer. Interfacial heat transfer and bulk overheating play dominant roles below and above a specific temperature threshold, respectively. Bubble growth is primarily driven by overcoming potential energy barriers between water molecules, which is enhanced under a high imposed driving force. Hydrophilic surfaces promote kinetic energy conversion, whereas hydrophobic surfaces reduce potential energy constraints. An activation energy equation is derived through microscale nucleation theory. The critical activation energy for heterogeneous nucleate boiling decreases with increased substrate wettability. Conversely, nucleation is suppressed under a high driving force by increasing the critical activation energy. This work would help understand the characteristics and mechanisms of flow boiling bubble behavior on zirconium metal substrates.

The helical-coiled once-through steam generator (H-OTSG) has been extensively adopted in small modular reactors such as lead-bismuth cooled fast reactors. Flow instability arising within helical tubes seriously affects the design of reactors and poses a severe challenge to their safety. This paper reports experiments on flow instability in a single helically coiled tube and subsequently analyzes the transient characteristics when flow instability occurs, and reveals the influence mechanism of flow instability. The results show that during the power increment process, density wave oscillations (DWO) are triggered once the heat flux exceeds 115 kW/m2 and markedly amplifies the non-uniformity of circumferential wall temperature distribution. The evolution of wall temperature when flow instability occurs indicates that the standard deviation of wall temperature is 2.5 times that under stable conditions and exhibits a strong positive correlation with mass flow oscillations. This confirms that the vapor phase lateral aggregation effect driven by secondary flow is the key factor in enhancing the heterogeneity of circumferential heat transfer. The influence of thermal hydraulic parameters (pressure, flow rate and inlet subcooling) on threshold power is also discussed. This paper analyzes the transient response characteristics of flow instability, explores the influencing factors of the flow instability boundary and proposes methods to suppress the occurrence of flow instability phenomena, providing a theoretical reference for the design and safety analysis of H-OTSG.

Dryout phenomena in helical-coileded steam generator tubes represent a critical limiting factor in thermal performance and operational safety. In this study, the initial dryout is examined through a combined experimental and theoretical approach, with particular focus on the influence of thermohydraulic parameters and vapor-liquid two-phase interactions on the critical vapor quality. Results indicate that dryout vapor quality is strongly correlated with the distribution of the annular liquid film, the intensity of secondary flows, and interfacial shear forces. Parametric sensitivity analyses reveal that increasing the inlet mass flux promotes liquid film redistribution under centrifugal effects and enhances secondary flow strength, thereby reducing the vapor quality at dryout. Conversely, higher pressure conditions suppress vapor expansion and void fraction, resulting in delayed dryout at elevated vapor qualities. The interfacial shear force, quantified using the slip ratio, exhibits a monotonic inverse relationship with dryout vapor quality, underscoring the role of secondary vapor flows in accelerating liquid film collapse. To further characterize the interaction between vapor-phase secondary motion and wall-adhering liquid films, a Centrifugal Punch Shear Interface (CPSI) analysis is proposed. Based on the analysis of interfacial interaction behavior, dimensionless parameters are introduced to quantify the effects of liquid film distribution, secondary flow patterns, and interfacial shear intensity on dryout. A predictive model for the critical vapor quality at initial dryout is developed based on these factors, achieving agreement with experimental data within a 15% deviation.

Fretting wear behavior of additively manufactured 316L stainless steel (AM 316L SS) was systematically investigated in argon atmosphere over 300-900°C using a self-developed high-temperature fretting wear rig. The results show that at all temperatures, the wear scars exhibit a gradient structure consisting of a third‐body layer (TBL), a plastic deformation layer (PDL), and the matrix. Wear volume increased monotonically with temperature. However, at 700°C, the Fe/Cr‐containing oxidative debris undergoes agglomeration, sintering, and cyclic compaction to form a relatively continuous TBL, which mitigates local penetration and promotes lateral expansion of damage, resulting in a non‐monotonic variation of the maximum wear depth. In the range of 300-500°C, the PDL mainly undergoes dislocation accumulation, mechanical refinement, and subgrain rotation; at 700°C, ultrafine grains coexist with recrystallized grains, with no significant change in average grain size; at 900°C, high‐temperature thermal softening, recrystallization grain coarsening, and TBL fragmentation jointly weaken the subsurface load‐bearing capacity, leading to aggravated wear. These findings provide mechanistic insights into high-temperature fretting wear of AM alloys and inform the design of wear-resistant structural components for inert environments.