Search Results (302)

In this study, the influence of precipitated Laves particles on the metastable pitting of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 refractory high-entropy alloys (HEAs) in 3.5 wt.% NaCl solution was investigated. Microstructures and corrosion behaviors were characterized by XRD, SEM, TEM, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS), and the underlying mechanisms were elucidated. The PDP test results demonstrate that the precipitated Laves particles reduce the pitting resistance of HEAs. The corrosion current densities of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 HEAs are 0.066 and 1.361 μA/cm², respectively, and the pitting potentials are 1.058 and 0.881 V, respectively; that is, reducing the Laves-particle content lowers the corrosion current density by a factor of approximately 20 and raises the pitting potential by approximately 180 mV. The corrosion current density and pitting potential of VCrFeTa_0.1W_0.1 are competitive with those of reported HEAs and traditional alloys. Full article

To address the problem of the short service life of relay injection molds caused by erosion of high-temperature glass fibers, AlCrN coatings were deposited on the surface of ELMAX mold steel using multi-arc ion plating technology. The surface morphology, cross-sectional morphology, and elemental composition of the coatings were analyzed using scanning electron microscopy (SEM) and the attached energy-dispersive X-ray spectroscopy (EDS). The phase structure was characterized by X-ray diffraction (XRD). The surface hardness, film–substrate adhesion strength, and friction and wear performance were tested using a nanoindenter, a scratch tester, and a friction and wear tester, respectively. The effects of duty cycle, arc current, and negative bias voltage on the coating microstructure, hardness, adhesion strength, and friction and wear performance were systematically investigated. Increasing the duty cycle increases surface particles and pits but improves coating density; increasing the arc current increases coating thickness but coarsens particles; increasing the negative bias voltage refines particles but increases pits. Through a three-factor, three-level orthogonal experiment and a multi-index equal-weight weighting method, with hardness, adhesion strength, and friction coefficient as comprehensive evaluation objectives, the optimal process parameters were determined as a duty cycle of 70%, an arc current of 60 A, and a negative bias voltage of 110 V. The optimized coating achieved a hardness of 36.04 GPa (399% higher than that of the uncoated substrate), an adhesion strength of 143.87 N, and a friction coefficient of 0.422. In production cycle tests, the coated mold exhibited an average service life of 128,070 cycles, which is 277% higher than that of the uncoated mold (33,985 cycles). The surface of the coated mold showed only slight scratches, while the uncoated mold exhibited severe glass-fiber plowing grooves. This study provides a process optimization and verification solution for extending the service life of injection molds. Full article

Ti-6Al-4V alloy possesses excellent specific strength, corrosion resistance, and biocompatibility, rendering it widely applicable in aerospace, marine engineering and biomedical fields. Selective laser melting (SLM) serves as an effective technique for manufacturing complex Ti-6Al-4V components. However, SLM-formed specimens generally suffer from surface defects such as high surface roughness, adhered powders, spheroidized particles, and localized spatter, which degrade their service performance and limit further practical applications. Therefore, effective surface modification is urgently required. This work systematically explores the synergistic effects of sandblasting at various angles followed by acid pickling on the surface characteristics of SLM-formed Ti-6Al-4V alloy. The SLM Ti-6Al-4V samples were first treated by sandblasting at different impact angles and then subjected to acid pickling. Material mass loss, micro-morphology, surface roughness, contact angle, surface microhardness, abrasive-particle embedment and surface residual stress were measured and analyzed. The results show that sandblasting angle exerts a remarkable influence on material removal behavior, abrasive-particle embedment and near-surface mechanical response. Scanning electron microscopy (SEM) observations indicate that sandblasting at different angles can not only effectively eliminate surface-adhered powders, but also generate impact pits, cutting grooves, and ploughing marks whose morphologies vary with sandblasting angles. The subsequent acid pickling process further removes loose particles and sharp protrusions, and promotes the formation of microscale surface structures. Benefiting from the combined effects of mechanical sandblasting and chemical acid pickling, the alloy samples exhibit substantially reduced surface roughness and enhanced surface wettability. Meanwhile, sandblasting induces work hardening and thus increases surface microhardness and surface residual stress, while acid pickling regulates surface morphology and the state of the work-hardened layer to a certain degree. Overall, this study provides an economical, efficient, and industrially feasible composite surface modification approach to reduce surface roughness, enhance hydrophilicity, and tailor surface hardness of SLM Ti-6Al-4V alloy. Full article

AISI 316L stainless steel (316L SS) exhibits inadequate corrosion resistance in chloride-containing soils. Fe-based amorphous coatings (Fe-ACs), owing to their high Cr, Mo, and W contents and defect-free amorphous structure, are promising candidates for superior protection. In this work, the corrosion behavior of 316L SS and an Fe-based amorphous coating (Fe-AC) fabricated by high-velocity oxygen-fuel (HVOF) spraying was systematically compared by burial in Daqing saline soil (25% water content) with 0, 1.0, and 2.0 wt.% NaCl for 15–55 days. Corrosion rates were measured via mass loss, and surface morphology, elemental distribution, and phase constitution were characterized using OM, SEM/EDS, and XRD. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to assess passive-film stability and charge-transfer resistance. The Fe-AC consistently exhibited an extremely low corrosion rate (below 0.01 mm y⁻¹), nearly independent of NaCl concentration and exposure time, with only sporadic rust spots and the formation of a compact Cr/Mo/W-enriched passive film. In contrast, after 55 days in soil containing 2.0 wt.% NaCl, the 316L SS showed a corrosion rate of 0.0562 mm y⁻¹—six times that of the Fe-AC—accompanied by severe pitting (pit depth up to 3.6 mm) and loose corrosion products (γ-FeOOH and α-Fe₂O₃). Electrochemical tests confirmed that the charge-transfer resistance of the Fe-AC under the 0% NaCl condition reached 1.16 × 10⁶ Ω cm² and its breakdown potential exceeded 1.12 V, far outperforming 316L SS (2.30 × 10³ Ω cm² and 0.22 V, respectively). The novelty of this study lies in the systematic evaluation of the buried corrosion performance of HVOF-sprayed Fe-based amorphous coatings versus 316L SS in an actual saline soil and in elucidating the synergistic passivation mechanism of Cr, Mo, and W. This passive film effectively impedes chloride ingress and maintains high impedance over extended periods. Full article

In the Afşin–Elbistan coal seam in Türkiye, this study investigates the vertical distribution, enrichment features, and mineralogical controls of trace elements and rare earth elements (REEs). Thirty coal samples were collected vertically from the Kışlaköy open-pit mine. Major oxide concentrations were determined by XRF for 29 samples, whereas trace element concentrations were determined by ICP–MS for all 30 samples. Mineralogical and textural characteristics were investigated in 15 selected samples by XRD and SEM–EDS. The coal is abundant in quartz, pyrite, and gypsum, along with trace amounts of calcite, clay minerals, and feldspars, which demonstrate the combined effects of detrital input, reducing depositional conditions, and post-depositional alteration. The major oxide composition is dominated by SiO₂, CaO, Al₂O₃, and Fe₂O₃, showing notable contributions from carbonate, aluminosilicate, and Fe-bearing mineral phases. Most trace elements occur at levels close to the world coal average, whereas V, Ni, and U are significantly enriched, and Cr and Co are slightly enriched. Total REE contents range from 21 to 125 ppm, averaging 51 ppm, and display light REE enrichment over heavy REEs. Weak negative Ce anomalies and slight positive Eu anomalies indicate variable redox conditions and the influence of terrigenous mineral input. Vertical distribution patterns indicate that during peat accumulation and early diagenesis, variations in detrital input, mineral matter abundance, and depositional redox conditions regulated trace element and REE distributions. REEs are mainly associated with aluminosilicate and locally phosphate-bearing phases, whereas V, Ni, and U are linked to organic matter and/or sulfide-rich intervals. These results show that the main factors influencing trace-element and REE behaviour in the Afşin–Elbistan coal seam are the mineralogical composition and redox evolution. Full article

The long-term reliability of XLPE submarine cable insulation is influenced by progressive thermal degradation during operation and subsequent seawater ingress caused by external damage. Although thermal aging and seawater exposure have been widely investigated individually, the influence of the prior thermal-aging state on the subsequent seawater-induced degradation behavior of XLPE remains insufficiently understood. In this study, XLPE insulation specimens prepared from the same commercial compound used for 500 kV submarine cables were subjected to sequential accelerated aging consisting of controlled thermal pre-aging followed by simulated seawater exposure. Broadband dielectric spectroscopy, AC breakdown testing with two-parameter Weibull analysis, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were employed to investigate the evolution of electrical properties, surface morphology, and molecular structure. The results demonstrate that seawater-induced electrical deterioration strongly depends on the initial thermal-aging state of XLPE. Increasing thermal pre-aging duration resulted in progressively higher relative permittivity and dielectric loss, together with reduced characteristic breakdown strength after subsequent seawater exposure. Under the most severe condition of 1440 h thermal pre-aging followed by 672 h seawater exposure, the power–frequency relative permittivity increased by 32.1%, while the characteristic breakdown strength decreased by more than one-third compared with the initial state. SEM observations revealed that thermally pre-aged specimens developed accelerated surface damage during seawater exposure, including pores, cracks, corrosion pits, and honeycomb-like structures. FTIR analysis further indicated molecular-chain degradation and increased hydroxyl-related species during sequential aging. These results suggest that thermal-aging-induced molecular oxidation, polar-group formation, and microstructural defects enhance water and ion penetration pathways, thereby increasing the susceptibility of XLPE insulation to subsequent seawater-induced degradation. This study provides material-level experimental evidence for understanding sequential aging processes in submarine cable insulation and highlights the importance of considering historical thermal damage in future condition assessment and lifetime evaluation models. Since accelerated laboratory conditions were adopted, the results should be interpreted as comparative degradation characteristics rather than direct predictions of field-service lifetime. Full article

The cavitation jet is regarded as a promising hydraulic rock-breaking technique for drilling and exploiting deep-sea natural gas hydrate (NGH). However, the detailed mechanisms of erosion pit formation in hydrate-bearing sediments (HBSs) under cavitation jet erosion remain unclear, and effective simulation methods are still limited. This study first conducts jet erosion experiments on HBSs using a convergent–divergent cavitation jet nozzle (CDCJ) and a conical jet (CJ) nozzle to evaluate the erosion performance of the CDCJ. The CDCJ is then applied to erode HBS specimens under different flow rates, erosion times, and stand-off distances, with the geometric characteristics of the erosion pits recorded. Subsequently, a coupled CFD-DEM framework is developed to further investigate the erosion process and mechanisms. Based on this model, the erosion characteristics of the cavitation jet at different stages and under varying jet parameters are analyzed and validated. The results show that the CDCJ exhibits a significantly stronger erosion capacity than the CJ, with the pit volume and depth reaching 1.36 and 1.19 times those produced by the CJ, respectively. The hole-forming process induced by the cavitation jet can be divided into three stages: the V-shaped hole-forming stage, the cylindrical hole-forming stage, and the spindle-shaped hole-forming stage. In the V-shaped hole-forming stage, jet impingement and the penetrating erosion of cavitation clouds dominate pit development. As erosion progresses, the axial impingement gradually weakens, whereas radial cutting decays more slowly. Meanwhile, vortices inside the pit trap cavitation clouds and promote further hole enlargement. Both the experiments and simulations indicate that higher flow rates produce larger and deeper pits, and a standoff distance of 5 mm is optimal for cavitation erosion. These findings clarify the hole-forming mechanism and flow-field evolution during the cavitation erosion of HBSs, and provide guidance for the application of the cavitation jet in NGH drilling and exploitation. Full article

In order to enhance the contact fatigue performance of the Cr12Mo1V1 die steel component, the ultrasonic impact surface-modification process was introduced into the heat treatment process of 1060 °C quenching + cryogenic treatment (−150 °C × 2 h) + two times of tempering at 520 °C × 2 h in this paper. The influence of the ultrasonic impact number on the surface morphology, roughness, micro-hardness value, residual stress, microscopic morphology of spalling pits, contact fatigue life, and EBSD inverse pole figure of the Cr12Mo1V1 die steel component were investigated utilizing a laser confocal microscope, 3D laser confocal microscope, micro-hardness tester, X-ray stress meter, scanning electron microscope, rolling contact fatigue testing machine, and EDAX-TSL system equipped with a field-emission scanning electron microscope, respectively. In comparison to other ultrasonic impact numbers, the Cr12Mo1V1 die steel component owned the smallest roughness of 0.027 μm, the highest micro-hardness value of 867 Hv_0.1 and the largest residual compressive stress of −1318 MPa, respectively. Meanwhile, the contact fatigue life of the Cr12Mo1V1 die steel component was significantly improved by 223% to 5.231 × 10⁷ cycles. After ultrasonic impact treatment, the spalling pits revealed that the crack propagation angle increased from 28° to 34°, the depth increased from 153 μm to 175 μm, and the failure mode consisted of Hertz’s contact theory. This study provides an effective surface strengthening solution for enhancing the contact fatigue performance of Cr12Mo1V1 die steel components. Full article

Background/Objectives: One-piece (monoblock) dental implants are increasingly used, particularly in patients with limited bone availability. Prosthetic alignment is often achieved via plastic deformation of the titanium implant. This study aimed to evaluate the impact of such deformation-induced residual stress on the corrosion resistance of these implants. Methods: Two types of monoblock dental implants (spherical “S” and Mag-Conical “M”) were subjected to controlled plastic deformation. Residual stress was quantified by X-ray diffraction using the Bragg–Brentano method. Electrochemical behavior was evaluated by measuring the open-circuit potential (E_OCP) and performing potentiodynamic polarization tests in phosphate-buffered saline (PBS) at 37 °C. Metal ion release (Ti, V, Al) was quantified by inductively coupled plasma mass spectrometry (ICP-MS) at specific immersion time points. Surface morphology and corrosion features were examined by scanning electron microscopy (SEM). Results: Residual stress values increased significantly after plastic deformation. The open-circuit potential (E_OCP) shifted towards more electronegative values in both implant designs as deformation-induced residual stresses increased. The E_OCP values shifted from −0.099 V to −0.227 V in the S design and from −0.115 V to −0.141 V in the M design, comparing the as-received condition with the deformed state, respectively. Potentiodynamic tests showed an increase in corrosion rate from 0.0021 mm/year for the original implants to 0.0156 mm/year for the deformed ones. Surfaces in the stressed regions exhibited a high density of corrosion pits, indicating localized electrochemical degradation. Deformed dental implants also exhibited higher ion release, particularly of titanium and vanadium, with higher levels observed in implants with greater residual stress and lower corrosion resistance. In the deformed regions, the release of titanium and vanadium ions into the surrounding medium was nearly five-fold higher. Conclusions: Plastic deformation of monoblock dental implants is associated with reduced corrosion resistance. Increased residual stress correlates with enhanced electrochemical degradation and ion release, which may have relevant implications for implant selection and clinical placement. Full article

Extreme wind events, particularly tropical cyclones, pose the most severe safety threat to aging lattice steel space-truss structures in coastal regions, including transmission towers, communication and observation towers, and lattice supports of building-integrated wind-energy facilities. Such structures suffer progressive capacity degradation through multiple concurrent mechanisms, yet their actual residual safety margin under extreme wind loading remains poorly quantified. Current assessment practices rely on code-prescribed simplified wind speeds that ignore terrain-induced local amplification, and assume an intact structural condition that neglects in-service deterioration. This paper proposes a Risk-Based Safety Assessment Framework (RBSAF) that addresses both deficiencies through a five-step pipeline: (i) multi-scale wind field downscaling that resolves terrain-amplified wind profiles at individual structure sites; (ii) independent degradation models for atmospheric corrosion, bolt loosening, fatigue accumulation, and pitting corrosion; (iii) a multi-degradation coupling aggregation method that yields a unified Structural Health Index (SHI) capturing nonlinear interaction effects; (iv) code-based multi-scenario safety margin scanning with automatic identification of weak components; and (v) a risk-informed reinforcement priority mapping strategy. A representative 220 kV angle-steel lattice tower in a coastal mountainous corridor of Southeastern China is employed as the case study. Results show that after 30 years of service in an ISO 9223 C4 corrosive environment, the structure-level SHI decreases from 1.47 (intact, code wind) to 1.00 under the proposed coupled assessment with code-prescribed wind, and further to 0.76 when terrain amplification (15% speed-up) is considered, with the failure probability rising from 3.6% to 24.1%. Multi-degradation coupling causes an additional 28% capacity loss relative to single-factor assessment and substantially alters the weak-component ranking. Reinforcing the five most critical members restores the SHI to 1.25 with only a 2.8% steel-weight increase. The framework provides a systematic, quantitative tool for safety evaluation and maintenance prioritization of aging lattice steel structures in wind-prone built environments. Full article

This study investigates the mechanical properties and corrosion behavior of a Co-free Fe₄₀Ni₃₀Cr₂₀V₈Mo₂ (at.%) multi-principal elements alloy (MPEA) designed for potential applications in aggressive environments. The alloy exhibits a balanced combination of strength and ductility, with a yield strength of approximately 258 MPa, an ultimate tensile strength of about 647 MPa, and a fracture elongation of around 52%, of which deformation is primarily governed by dislocation-mediated plasticity. In terms of corrosion performance, the alloy demonstrates excellent resistance in chloride-containing environments. Potentiodynamic polarization tests reveal a wide and stable passive region of approximately 1.28 V_SCE and a high pitting potential of about 0.975 V_SCE, indicating exceptional stability of the passive film. Electrochemical impedance spectroscopy (EIS) further confirms the high impedance and protective nature of the surface layer. X-ray photoelectron spectroscopy (XPS) analysis reveals that the superior anti-corrosion property is attributed to the formation of a passive film enriched with protective Cr₂O₃ and V, Mo oxides, which collectively construct an effective barrier against chloride-induced attack by reducing donor density. This work provides valuable insights for the development of alternative alloys to replace Co-containing systems in demanding corrosive applications. Full article

Pituitary apoplexy is an uncommon but clinically urgent complication that often involves intrasellar hemorrhage and tissue necrosis. The mechanisms linking acute tissue injury to the inflammatory tumor microenvironment remain incompletely defined. Here, we characterized the apoplexy-associated microenvironment and examined whether macrophage mechanosensitive signaling contributes to inflammatory amplification and tissue damage in pituitary neuroendocrine tumors (PitNETs). We combined single-cell RNA sequencing (scRNA-seq), histological validation, clinical stratification, and in vitro functional assays using apoplectic and non-apoplectic human PitNET specimens. Macrophage state transitions, intercellular communication, and transcriptional regulatory programs were analyzed, followed by an experimental assessment of the PIEZO1–Ca²⁺ axis and macrophage-conditioned medium-induced tumor cell death. Histological validation confirmed macrophage accumulation in apoplectic PitNETs, including a 1.67-fold increase in IBA-1-positive cells (p < 0.001). CellChat-inferred interaction metrics increased descriptively in apoplectic samples. Apoplectic tissues showed higher TNF-α expression (3.00-fold; p < 0.0001) and higher PIEZO1 fluorescence in IBA-1-positive regions (1.39-fold; p = 0.001). Yoda1 increased Calcium 520 fluorescence in macrophages (1.72-fold; p = 0.002), whereas Piezo1 knockdown reduced the Yoda1-associated response (p = 0.003). Conditioned medium from activated macrophages increased total Annexin V/PI-positive death in AtT-20 cells (0.53 ± 0.53% to 32.48 ± 1.14%; p < 0.001) and GH3 cells (0.82 ± 0.50% to 30.92 ± 1.11%; p < 0.001); Piezo1 knockdown or TNF-α neutralization attenuated this effect. Clinically, pathological necrosis was associated with higher symptom frequencies and a greater adjusted likelihood of two or more clinical symptoms. Together, these findings indicate that PIEZO1-related macrophage signaling may participate in TNF-α-associated tumor cell necroptosis in pituitary apoplexy. Pathological necrosis was linked to greater acute symptom burden and perioperative hormonal abnormalities, suggesting that it may identify a clinically severe apoplexy subtype. Full article

Cameras and IMUs on heavy mining trucks supply the visual signal that Advanced Driver Assistance Systems (ADASs) use in open-pit operations. Haul roads in a surface mine are unstructured and unmarked, so a perception model must be both accurate and fast. We address this with a video-based multitask pipeline for a mining Driver Support System (DSS): a single BiSeNetV1 network produces drivable-area segmentation and steering-direction classification in one forward pass. Training used only 100 frames sampled non-sequentially from in-cab recordings of a real open-pit mine; evaluation used two full onboard sequences. To exploit temporal redundancy without annotating video, we propose an Adaptive Clockwork (A-CW) inference scheme: the spatial path runs on every frame, while the context path is refreshed only on keyframes whose cadence is set by the classification output, the same signal shown to the driver as a steering hint. This classification-guided policy increases context updates on curved segments, where the scene changes more rapidly, and reduces them on straight sections, where semantic redundancy is higher. The selected A-CW configuration was evaluated on full temporal test sequences, including one route kept entirely outside the training source. On this unseen route, A-CW achieved 94.70% road-class IoU and 73.68% Top-1 Accuracy. GPU-only throughput increased from about 55 FPS with frame-by-frame inference to 168.01 FPS, and display-excluded end-to-end processing in the simulated ADAS pipeline remained at approximately 37.5 FPS. Full article

Background/Objectives: Accurate pT1b diagnosis in colorectal cancer is vital owing to the risk of lymph node metastasis. While Japan NBI (narrow band imaging) Expert Team (JNET) classification is widely applied, accurate diagnosis of type 2B lesions remains challenging, often requiring pit pattern analysis via magnifying chromoendoscopy with crystal violet staining (MCE). However, the clinical application of MCE is limited by potential carcinogenicity and prolonged procedure time. In this study, we aimed to evaluate the diagnostic performance of red dichromatic imaging with indigo carmine (RDI-indigo) in assessing the invasion depth of colorectal tumors. Methods: Ninety images were obtained from 30 colorectal tumor cases using RDI-indigo, NBI, and MCE. Six endoscopists classified images using JNET classification for NBI, and pit pattern classification for RDI-indigo and MCE. JNET type 3 and pit pattern classification V irregular, high grade/V non-structure were correlated with pathological depth ≥pT1b. The primary outcome was the diagnostic accuracy for ≥pT1b. Results: Diagnostic accuracies for ≥pT1b were 85.0% (95% CI: 79.8–90.2%) for RDI-indigo, 79.4% (95% CI: 73.5–85.3%) for NBI, and 82.8% (95% CI: 77.3–88.3%) for MCE. Intraobserver agreement between RDI-indigo and MCE showed fair agreement (Cohen’s kappa = 0.39), while interobserver agreement was moderate for MCE (Fleiss’ kappa = 0.56) and fair for RDI-indigo (Fleiss’ kappa = 0.36). Gwet’s AC1 indicated substantial agreement across all assessments (0.69–0.80). Conclusions: As the first report evaluating RDI-indigo for colorectal tumors, this study suggests that RDI-indigo could serve as a complementary MCE-like tool for the diagnosis of ≥pT1b lesions. Full article

Transmission Electron Microscopy (TEM) requires electron-transparent samples with thickness below 100 nm, and conventional preparation methods involving mechanical polishing followed by electropolishing or ion milling are time-consuming and prone to preparation-induced defects. In this study, an electrothinning process was proposed as an alternative intermediate TEM sample preparation technique. Electrothinning was carried out on 1 mm thick equiatomic NiTi alloy using H₂SO₄ (20%) and methanol (80%) electrolyte at an operating voltage of 10–15 V for 20 min. The sample thickness was reduced from 1 mm to 55 μm through controlled anodic dissolution without mechanical deformation. Uniform thinning behaviour was observed under optimized conditions, while lower voltages resulted in insufficient dissolution and higher voltages caused localized pitting. TEM analysis confirmed the absence of noticeable mechanically induced defects or deformation features in the electrothinned samples. The proposed method is a cost-effective and efficient alternative for TEM sample preparation in research and industry. Full article