Search Results (1,437)

CoCrFeNi/WC-Nb high-entropy alloy (HEA) composite coating was prepared on the surface of Q235 steel by LC (laser cladding) technology, and the effects of WC and in situ NbC reinforcement on the coating were studied. The phase composition, phase characteristics, microhardness, and wear resistance of the cladding coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), friction and wear tester, and X-ray photoelectron spectroscopy (XPS), and the corrosion resistance was tested by a three-electrode electrochemical workstation. The results show that the CoCrFeNi/WC-Nb HEA coating consists of FCC, WC, NbC, and Laves phases, and the reinforcing phase causes grain refinement and lattice distortion. The microhardness reached (418.29 ± 16.72) HV, which was about 2.64-times higher than that of the CoCrFeNi HEA coating. The wear rate decreased to (1.150 ± 0.11) × 10⁻⁴ mm³N⁻¹m⁻¹, which was about 0.25 times that of the CoCrFeNi HEA coating, and the wear of the coating changed from abrasive wear to adhesive wear. The corrosion current density and corrosion voltage of the CoCrFeNi/WC-Nb HEA coating are (3.3820 ± 0.2103) × 10⁻⁶ A/cm² and −(0.7650 ± 0.0850) V, respectively. Full article

This study investigates the influence of barrel filling ratio on the microstructure, phase composition, and tribological performance of detonation-sprayed Cr₃C₂–NiCr coatings. Coatings were deposited at barrel filling ratios of 43% and 53% under identical spraying conditions. Microstructural characterization revealed the formation of dense lamellar coatings with low porosity and uniform distribution of Cr₃C₂ carbide particles within the NiCr metallic matrix. Compared with the coating deposited at a barrel filling ratio of 43%, the coating deposited at 53% exhibited a denser microstructure. X-ray diffraction analysis confirmed that Cr₃C₂ and NiCr remained the dominant phases after spraying, while a minor amount of Cr₇C₃ formed due to partial decarburization of chromium carbide during thermal exposure. Tribological performance was evaluated under dry sliding conditions using a ball-on-disc configuration at normal loads of 10 and 15 N and sliding speeds of 5 and 10 cm/s. Wear volume was determined from the geometry of the wear track after testing, and wear rate was calculated accordingly. The coating produced at a barrel filling ratio of 53% demonstrated improved wear resistance under elevated loads despite exhibiting a higher coefficient of friction. The minimum wear rate reached 1.23 × 10⁻⁴ mm³/(m·N), which was associated with reduced porosity and enhanced structural integrity of the coating. The obtained results demonstrate that optimization of detonation spraying parameters significantly affects coating structure and tribological behavior. The developed Cr₃C₂–NiCr coatings are promising protective materials for components operating under severe friction and wear conditions, including industrial and high-temperature engineering applications. Full article

This study aims to investigate the effects of heterogeneous microstructure and strain rate on the microstructural evolution and mechanical properties of ultrafine-grained (UFG) austenitic stainless steel during elevated-temperature tension. In this research, 17Cr-10Ni austenitic stainless steel was rolled to a 60% reduction in thickness at room temperature and 200 °C, followed by annealing at 1000 °C and 500 °C, respectively. The microstructural evolution of the annealed samples and high-temperature tensile specimens was characterized using optical microscopy, transmission electron microscopy, scanning electron microscopy equipped with electron backscatter diffraction, and X-ray diffraction. Results show that at room temperature, the heterogeneous twinned UFG (TW-UFG) sample, influenced by hetero-deformation-induced stress strengthening, maintains good ductility while exhibiting higher strength than the uniform UFG sample. During tensile deformation at 600 °C, grain refinement still contributes to strengthening, and the dominant deformation mechanism in the uniform UFG sample is dislocation dynamic recovery, whereas in the TW-UFG sample is detwinning combined with dynamic dislocation recovery. At low strain rates (10⁻⁴ s⁻¹), sufficient dynamic recovery and detwinning in the TW-UFG sample delay plastic instability and improve elongation. Full article

High-temperature corrosion severely impairs the service life of boiler heating tubes and threatens the safe and economical operation of thermal power units. With diversified fuels (coal, biomass and refuse-derived fuels) and continuously elevated operating parameters (steam temperature exceeding 620 °C for ultra-supercritical units), boiler heating surfaces are exposed to increasingly complex corrosive environments. High-temperature oxidation, sulfidation, chlorination, molten salt hot corrosion and deposit-induced multi-factor coupled corrosion coexist and exacerbate each other. This paper adopts a four-dimensional analytical framework of “mechanisms–technologies–materials–evaluation” to systematically summarize relevant research progress. From the perspective of corrosion mechanisms, the evolution of understandings from single high-temperature oxidation to multi-factor coupled corrosion is reviewed. In terms of surface coating technologies, seven mainstream processes including HVOF/HVAF spraying, plasma spraying, cold spraying, laser cladding and weld overlay are compared in terms of preparation characteristics and engineering applicability. For coating materials, twelve material systems such as NiCr alloys, MCrAlY, cermets, Fe-based amorphous/nanocrystalline alloys and high-entropy alloys are evaluated for their corrosion resistance under diverse service conditions. As for monitoring and evaluation, this work introduces full-range corrosion management technologies covering electrochemical monitoring, non-destructive testing, numerical simulation and life assessment. Finally, the paper discusses the application prospects of gradient coating design, AI-assisted material screening and digital twin technology, and points out key research gaps including long-term service reliability verification of coatings and quantitative prediction models for multi-factor coupled corrosion. Full article

To overcome the insufficient hardness and wear resistance of CoCrFeNi alloy coatings under heavy-load conditions, CoCrFeNi-TiC composite coatings with varying TiC mass fractions were fabricated on a 42CrMo substrate using laser cladding. The present study systematically investigates the effects of TiC content on phase composition, microstructural evolution, microhardness, and tribological behavior. The results show that TiC addition does not change the primary phase constitution of the face-centered cubic (FCC) matrix, but induces lattice distortion and grain refinement, resulting in a pronounced enhancement of coating hardness. As the TiC content increased, the average microhardness rose from 222.9 HV_0.2 to 380.9 HV_0.2, which was 1.7 times that of the coating without TiC. The enhanced hardness is mainly attributed to grain refinement, solid-solution strengthening, and the dispersion effects of TiC particles. The tribological performance showed a non-monotonic dependence on TiC content. Among the tested samples, the coating with 10 wt.%TiC showed the best wear resistance, with an average friction coefficient of 0.56 and a wear rate of 1.15 × 10⁻⁴ mm³/(N·m). However, further increasing the TiC content to 15 wt.% slightly reduced wear resistance because particle spalling promoted three-body abrasive wear. These results indicate that an appropriate TiC content can improve the balance between hard-phase strengthening and wear stability of CoCrFeNi-based composite coatings. This work clarifies the microstructure regulation and wear failure mechanism of TiC-reinforced coatings, providing experimental guidance for heavy-load service coating design. Full article

High-temperature low-pressure carburizing significantly reduces the time required to produce carburized layers. However, its application promotes austenite grain growth and, consequently, the formation of coarse acicular martensite. In this study, the possibility of limiting this phenomenon in AMS 6265 and 18CrNiMo7-6 steels using the PreNitLPC^® technology was evaluated. The process was carried out at 1050 °C, with pre-nitriding applied during charge heating. In both steels, comparable carbon concentration profiles and carburized layers with an effective case depth of approximately 1.0 mm were obtained. The introduction of nitrogen into the surface layer resulted in a local reduction in austenite grain growth compared with the core. The average grain size in the surface layer was approximately 14.5 µm for AMS 6265 steel and 12.5 µm for 18CrNiMo7-6 steel, whereas in the core it increased to approximately 25.1 µm and 24.1 µm, respectively. At the same time, AMS 6265 steel exhibited a higher fraction of retained austenite, approximately 20%, compared with approximately 15% for 18CrNiMo7-6 steel. This resulted in a lower near-surface hardness of AMS 6265 steel, approximately 750 HV0.1, compared with approximately 800 HV0.1 for 18CrNiMo7-6 steel, corresponding to a hardness difference of about 50 HV0.1. TEM/NBD/EDS investigations showed that nanoscale AlN precipitates formed in both steels and acted as the main factor inhibiting austenite grain-boundary migration. The results confirm that the PreNitLPC^® technology enables high-temperature low-pressure carburizing without detrimental grain growth in the surface layer. Full article

Road dust is an important urban reservoir of potentially toxic elements (PTEs) and a relevant source of human exposure through resuspension and inhalation, particularly in large megacities. This study provides an integrated assessment of the seasonal variability, contamination levels, source identification, particle characteristics, lung bioaccessibility, and health risk of road dust in Mexico City, one of the world’s largest urban centers. A total of 74 road dust samples were collected during the dry and wet seasons, and V, Cr, Mn, Co, Ni, Cu, As, Cd, Sb, and Pb were analyzed by ICP–MS in the <20 µm fraction. Geochemical indices, spatial analysis, Pearson correlation, principal component analysis, SEM–EDS particle characterization, in vitro lung bioaccessibility (ALF), and human health risk models were applied. Sb, Cu, and Pb were identified as the most enriched elements, exceeded local background concentrations at all sampling sites. Spatial patterns revealed recurrent hotspots in the northern, northeastern, and central sectors of the city. SEM–EDS analyses showed that most particles belonged to the 2.5–5 µm equivalent-size class and included Fe-rich spherules, Pb-rich aggregates, silicate grains, and C-rich particles. Health risk assessment indicated acceptable risks for adults, whereas children exceeded the non-carcinogenic threshold (HI = 3.85–4.60) and slightly surpassed the upper acceptable carcinogenic risk level. Lung bioaccessibility results revealed low Pb solubility but high mobility of Ni and Cu, with some samples reaching complete dissolution under ALF conditions. These findings demonstrate that traffic-derived road dust represents a persistent urban exposure pathway in Mexico City and highlight the importance of integrating total concentrations, particle characteristics, and bioaccessibility data to improve environmental and health-risk assessments in urban environments. Full article

The curing quality of epoxy resin at wind turbine blade joint seams critically affects blade integrity and service reliability, yet conventional metallic heating systems often suffer from poor temperature uniformity, limited flexibility, and slow thermal response. In this study, a flexible and lightweight heating blanket based on carbon nanotube (CNT) electrothermal film was developed for blade reinforcement and in situ curing applications. The device employs a multilayer composite architecture consisting of a CNT heating layer, a nano-aerogel thermal insulation layer, a thermoplastic polyurethane electrical insulation layer, and a silicone-coated glass fiber protective layer, together with an intelligent temperature control system. The resulting blanket, with a total thickness of 3.85 mm, exhibited rapid and stable heating performance, increasing from 25 to 120 °C within 8 min. Under resin-curing conditions, it achieved an initial heating rate of 7.2 °C min⁻¹ and a temperature uniformity of ±2.6 °C, markedly outperforming a conventional Ni@Cr alloy heating blanket. Accelerated aging tests further demonstrated stable electrothermal performance under the tested condition. Those results indicate that the proposed CNT-based heating blanket provides an efficient and reliable thermal management strategy for large curved composite structures. Full article

In this work, ternary Mo–Ni–X (X = Al, Co, Cr, Cu, Fe, W) thin films with nominal composition Mo₈₀Ni₁₀X₁₀ (at. %) were prepared by magnetron sputtering and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. The influence of alloy composition, substrate type, and deposition temperature on catalytic performance was systematically investigated. Electrochemical screening revealed a strong dependence of HER activity on both substrate conductivity and ternary alloying, with Al-, Cr-, and W-containing systems showing the best performance on glassy carbon substrates. This highlights the importance of interfacial charge-transfer efficiency in determining catalytic behavior. The Mo₈₀Ni₁₀Cr₁₀/GC system was selected for detailed analysis. Deposition temperatures ≥ 500 °C resulted in enhanced HER activity, reaching an overpotential of η₁₀ = −222 mV at j = −10 mA cm⁻². The improved performance is attributed to temperature-induced microstructural optimization and electrochemically driven surface reconstruction, leading to the formation of a Ni-enriched active interface. AFM analysis confirmed surface restructuring during operation, with roughness increasing from ~1 to ~3 nm, indicating the formation of additional electrochemically accessible active sites. XPS results suggest partial depletion of Mo during cycling, while Cr mainly contributes to structural stabilization of the evolving thin film. Overall, the results demonstrate that HER performance is governed by the coupled effects of alloy composition, substrate-dependent charge transport, and in situ surface reconstruction. This work highlights magnetron sputtering as a scalable approach for designing homogeneous noble-metal-free thin-film electrocatalysts with tunable activity. Full article

Graphene-reinforced CrCoNiFeMo high-entropy alloy composite coatings were fabricated on 17-4PH stainless steel by laser cladding for the surface protection of industrial robotic end-effector grippers. The effects of graphene content on microstructure, hardness, wear behavior and corrosion resistance were investigated. Graphene-derived carbon suppressed Laves and σ phases and promoted the in situ formation of M23C6, M7C3 and Co2C carbides, transforming the coating into a carbide-reinforced FCC/BCC composite structure. The average hardness increased from 462 HV0.2 to 676 HV0.2 with increasing graphene content. The 0.4 wt.% graphene coating showed the best wear resistance, with the lowest friction coefficient of 0.42 and minimum wear scar width and depth of 546 μm and 5.72 μm, which was attributed to carbide strengthening and the possible formation of a carbonaceous lubricating tribo-layer. The 0.2 wt.% graphene coating exhibited the best corrosion resistance, with the lowest corrosion current density of 5.81 μA/cm² and the highest impedance response. Excessive graphene caused carbon-rich agglomeration, excessive carbide precipitation and weakened passivation. This work provides a feasible surface strengthening strategy for 17-4PH stainless steel robotic gripper components. Full article

Petroleum exploitation in the Niger Delta has caused widespread contamination of mangrove ecosystems, yet studies that integrate total petroleum hydrocarbons (TPH) and metals in mangrove water are still very limited. This study presents the first dual-pollutant baseline assessment of TPH and five priority metals (Cd, Cr, Pb, Ni, Zn) in Bille mangrove water, a severely oil-impacted system supporting about 50,000 residents. Water samples were collected from six sites along a contamination gradient (flow station, pipeline passage, old bunkering site) and analyzed for TPH (C8–C40) and metals. All concentrations are reported in mg/L for direct comparability with World Health Organization (WHO) drinking-water guidelines and United States Environmental Protection Agency (USEPA) thresholds. TPH concentrations ranged from 0.18 to 57.66 mg/L, with Site 3 (pipeline passage) showing levels about 320-fold higher than reference sites and exceeding the WHO drinking-water guideline (0.05 mg/L) by up to 1153-fold. Cadmium (0.040–0.350 mg/L) and nickel (0.055–0.561 mg/L) exceeded WHO drinking-water guidelines (Cd 0.003 mg/L; Ni 0.07 mg/L) by 13–117- and up to 8-fold, respectively. Health risk assessment, using USEPA Risk Assessment Guidance for Superfund (RAGS) protocols, revealed a total cancer risk of 4.15 × 10⁻³ at Site 3, 41-fold above the USEPA acceptable threshold of 1 × 10⁻⁴, and extreme non-carcinogenic risk (Hazard Index = 20.03–25.51) at petroleum-infrastructure sites; cadmium contributed 86–88% of both carcinogenic and non-carcinogenic effects. Ecological risk indices classified Site 3 as extreme (Potential Ecological Risk Index = 722, against the Håkanson PERI = 600 “very-high-risk” threshold), mainly driven by cadmium (Er = 310–350) and nickel (Er = 140–150). Source apportionment using the Carbon Preference Index, enrichment factors, and strong TPH–metal correlations (r > 0.88, p < 0.01) clearly identified petroleum operations as the dominant contamination source. This work demonstrates the critical importance of integrated multi-pollutant assessments in petroleum-degraded mangrove water for guiding environmental protection and public-health interventions. Full article

CoCrFeNi-based high-entropy alloys (HEAs) have shown great potential for widespread applications in aerospace, chemical, and medical equipment fields due to their high strength, wear resistance, corrosion resistance, and thermal stability. In the present study, a series of Ni₂CoCrFeV_xCu_y alloys were designed to obtain a ductile FCC matrix suitable for ceramic-particle reinforcement. Subsequently, two representative reinforcement strategies, namely, in situ TiC formation and direct TiN nanoparticle addition, were employed to investigate their effects on the microstructure and mechanical properties of the alloy. The results showed that Ni₂CoCrFeV_0.5Cu_0.2 exhibited the best strength–ductility balance, with a tensile elongation of 51.8% among the designed alloys. Besides, the comprehensive performance of high-entropy alloys can be effectively enhanced by in situ generation of TiC and addition of TiN particles. The in situ synthesized TiC exhibited a finer and more uniform distribution than the directly added TiN particles, resulting in a more favorable strength–ductility balance under the present processing conditions. Full article

Introduction: Establishing baseline descriptions of inorganic elements in the early life stages of sharks and in their respective nursery areas is essential for assessing anthropogenic impacts and supporting conservation strategies. Objectives: This study presents the first baseline of plasma trace element concentrations (Al, Zn, As, Cu, Cr, Cd, Co, Mn, Ti, Ni, Hg, Pb) for four juvenile shark species (Carcharhinus limbatus, Paragaleus pectoralis, Rhizoprionodon acutus, and Sphyrna lewini) from Sal Rei Bay, Boa Vista Island, Cabo Verde—the first multi-species shark nursery area described in Atlantic Africa. Methodology: Seawater and sediment samples were collected from eight sites and analyzed along with plasma samples using total reflection X-ray fluorescence spectroscopy (TXRF). Sediment granulometry and pollution indices, including the enrichment factor (EF), ecological risk index (RI), and metal pollution index (MPI), were used to characterize habitat contamination. Data were analyzed using statistical models to explore spatial and element-specific patterns. Results: Overall, environmental contamination was low, with slight increases in Cd, Co, and Hg at sites 1 and 2, near the fishing port, and at site 5, likely reflecting natural transport, sediment redistribution, and enhanced nearshore deposition. Juvenile sharks exhibited generally low plasma trace element concentrations, although species-specific elemental signatures were evident: elevated levels of Al and Cu in C. limbatus, Zn in S. lewini, and As in R. acutus and P. pectoralis. Conclusions: These findings establish critical baseline reference values for trace elements in juvenile sharks from a key Atlantic nursery area. The results provide an essential framework for future biomonitoring efforts and contribute to the management and conservation of Cabo Verdean shark nursery habitats. Full article

Al_0.2CoCrFeNi-5%WC high-entropy alloy (HEA) composites were fabricated via spark plasma sintering at temperatures ranging from 900 °C to 1050 °C, and the effects of sintering temperature on phase constitution, microstructure, and mechanical properties were systematically investigated. The results show that all composites consist predominantly of an FCC matrix, WC, M₂₃C₆ and M₆C carbides. With increasing sintering temperature, interfacial reactions are promoted, leading to the progressive consumption of WC and an increase in carbide content. The composite sintered at 1000 °C achieves the optimal combination of properties, with a relative density of 96.8%, a yield strength of 468 MPa, an ultimate compressive strength of 1871 MPa, and a fracture strain of 43.6%. The outstanding strength–ductility synergy originates from near-full densification, robust interfacial bonding, and multiple carbide strengthening mechanisms. Excessively high sintering temperature (1050 °C) results in reinforcement coarsening and degradation of mechanical properties. Full article

Thin-film thermocouples (TFTCs) offer conformal sensing junctions with minimal thermal mass, enabling rapid transient response and direct deposition on curved or moving components, which are difficult to achieve using conventional wire thermocouples in applications such as high-speed machining, electric powertrain thermal management, and fuel-cell monitoring. In practical deployment, the effective accuracy of a TFTC can also be affected by the measurement setup used for calibration and testing, particularly lead-wire material transitions, cold-junction compensation, and wiring-related thermoelectric offsets. This study presents a systematic static calibration and performance evaluation of NiCr-based TFTCs under standardised laboratory conditions, with repeated measurements across the 20–260 °C range using both copper leads and matched compensation wires. The thermoelectric output exhibits excellent linearity; temperature reconstruction against a traceable standard reference yields a maximum deviation of approximately 0.27 °C, with root-mean-square and relative errors within tight bounds. Short-term extended-range verification up to 1000 °C confirms detectable thermoelectric signal generation under the present test conditions. A calibration data packet framework containing the calibrated TFTC sample, wiring configuration, calibration coefficients, validity range, and a GUM-compliant uncertainty budget is proposed to support consistent interpretation of calibration results in future digital integration. The study therefore provides a structured calibration workflow and uncertainty-reporting basis for the tested flexible NiCr-based TFTC configurations, supporting further reliability assessment, material-level characterisation, and digital integration. Full article