Search Results (1,528)

Carbon-fiber-reinforced silicon carbide (C/SiC) ceramic matrix composites (CMCs) exhibit substantial application potential in the field of advanced industrial manufacturing, attributed to their inherent superiorities such as high specific strength, excellent high-temperature resistance, and prominent corrosion resistance. Nevertheless, hole-exit delamination is a critical defect in C/SiC composite drilling, which impairs the structural integrity and service reliability of components, restricting their engineering implementation. To address this issue, this study proposes and systematically investigates a compressive stress-assisted drilling method for delamination suppression via applying external compressive stress. Using the delamination factor for quantitative evaluation, comparative experiments were conducted under unassisted drilling, graphite-plate-assisted drilling without preload, and graphite-plate-assisted drilling with varying preload torques. The results indicate that compressive stress significantly mitigates delamination, with a maximum delamination factor reduction rate of 18.29%. Mechanistically, the compressive stress effectively controls delamination by suppressing Mode I crack propagation at the crack tip and elevating the critical strain energy release rate. Furthermore, this work elucidates that the essential role of the graphite plate is to provide a controllable in-plane pre-compressive stress field for the workpiece drilling zone. Full article

Corrosion, salt deposition, and biofouling critically impair flow assurance and mechanical integrity in oil and gas production systems, resulting in escalating operating costs and environmental burdens. This study presents a screening-level multi-criteria decision-making framework grounded in petroleum engineering practice. Unlike conventional MCDA approaches that require extensive laboratory testing for each asset, our model enables the rapid assessment of inhibitor transferability between technologically similar fields using normalized field parameters and actual procurement data. The model integrates a correlation analysis of the key field parameters of temperature, acid gas content, salt concentration, flow velocity, and water cut with a weighted effectiveness coefficient. A dataset of operational records was coupled with factual procurement prices from 2020 to 2025 to simultaneously optimize inhibitor type and dosing. The novelty lies in the multiplicative weighting scheme and the concept of critical deviation thresholds, which allow engineers to identify cost-saving opportunities without compromising the 90% protection target. Application of the model presented in this article allows a reduction in annual chemical-related operational expenditures. The proposed methodology provides petroleum engineers with a robust, data-driven screening tool to design cost-effective chemical treatment strategies that maintain corrosion protection and reduce environmental load, thereby advancing oil field chemistry technology and supporting efficient oil and gas field development. Full article

A CT-80 coiled tubing fractured at the gooseneck during retrieval after a 2.5 h treatment with 15% HCl under high-temperature bottom-hole conditions (196 °C). The failure was investigated by dimensional measurements, metallography, Vickers microhardness testing, SEM/EDS, and FT-IR spectroscopy. Pronounced corrosion asymmetry was observed. Cumulative external wall loss reached 1.196 mm, compared with 0.292 mm on the inner wall, while the wall loss attributed to the final operation was approximately twelve times greater externally than internally. These findings suggest two different exposure histories: predominantly uniform attack of the outer wall during backflow of spent, inhibitor-depleted acid, and localized pitting of the inner wall under incomplete inhibitor coverage. EDS mapping identified Sb-rich deposits around inner-wall pits. In combination with the relevant literature, this distribution is consistent with a possible Sb–Fe galvanic effect that may have promoted local anodic dissolution, although galvanic coupling was not measured directly. The FT-IR spectra were consistent with iron oxides/oxyhydroxides, carbonate-containing scale, sulfate-bearing products on the outer surface, and thin organic residues rather than a continuous inhibitor film. Microhardness increased from 229 HV1 in the new tubing to 243.4 HV1 at the fracture location; this increase may reflect limited hydrogen uptake together with service-induced strain hardening or residual stresses. Fractography showed necking and dimpled microvoid coalescence, supporting a predominantly ductile overload mechanism in the corrosion-thinned section. A limited contribution of hydrogen to ductility loss cannot be excluded because the hydrogen content was not quantified. Full article

Rosin- and castor-oil-derived resins provide a renewable platform for rapidly curable protective coatings, but the effects of formulation and curing route remain insufficiently resolved. Four composite formulations containing modified rosin glycerol ester (MRGE) and modified castor oil anhydride (MCOA) were cured thermally using ultraviolet irradiation or electron beam (EB) irradiation. Surface C=C conversion, thermal behavior, morphology, mechanical properties, neutral salt spray resistance, electrochemical barrier performance, and AC dielectric breakdown strength were evaluated. Among the formulations tested, F2 (MRGE/MCOA = 3:1) showed the best overall property balance under each curing route. For F2, EB curing produced a surface C=C conversion of 92 ± 2%, a glass transition temperature of 88 ± 1 °C, an 800 °C residue of 12.5 ± 0.3%, and an atomic force microscope (AFM) roughness Ra of 5.8 ± 0.5 nm. F2-EB exhibited 9H pencil hardness, 5B adhesion, an impact resistance of 55 ± 2 cm·kg, and a flexibility value of 1.0 ± 0.1 mm. After 500 h of neutral salt spray, both F2-EB and F2-UV achieved a protection rating of 10 with no measurable corrosion creep at the scribe; time-resolved photographs at 100, 300, and 500 h confirmed that F2-EB showed the least visible damage evolution among the three curing routes. After 1 day of immersion in 3.5 wt% NaCl, F2-EB exhibited the largest low-frequency impedance and the lowest fitted corrosion current density among the EB-cured formulations, indicating the strongest short-term electrolyte barrier behavior. The AC dielectric breakdown strength of F2-EB reached 21.5 ± 0.3 kV mm⁻¹. The combined results are consistent with more extensive EB-induced network formation, although direct measurements of through-thickness conversion and crosslink density are still required. These findings demonstrate the potential of EB curing for rapidly preparing rosin/castor-oil-derived protective coatings for electrical insulation applications. Full article

Under complex terrains and extreme environmental conditions such as high wind speeds, prestressed rock anchor foundations for onshore wind turbines are subjected to multiple coupled adverse effects during long-term service, including cyclic wind loading, temperature variation, groundwater intrusion, and rock mass weathering. These factors significantly affect structural performance and service life through corrosion and material degradation processes, while conventional design methods mainly focus on ultimate bearing capacity and lack a systematic consideration of corrosion-induced deterioration mechanisms and long-term performance evolution. Without changing the theoretical framework of current design codes, this study introduces a durability-oriented design concept and explicitly incorporates corrosion effects and material degradation into the analytical system of prestressed rock anchor foundations. First, from the perspective of anchor force evolution, a time-dependent analysis method for long-term prestress loss is established, considering the coupled effects of steel corrosion, material relaxation, and cyclic loading. Second, for the mechanical behavior of group anchor systems, a shear capacity model is proposed that accounts for rock mass strength degradation and grout–rock interface deterioration. Meanwhile, the coupling relationship between foundation void development and groundwater seepage is analyzed, revealing its critical role in the corrosion evolution process. On this basis, a coordinated design method for foundation dimensions and prestress parameters is developed to satisfy both load-bearing capacity and durability requirements. Finite element analysis is further conducted to verify the stress and deformation characteristics of the foundation–rock–anchor system under nonlinear conditions. Engineering case studies demonstrate that the proposed method not only meets bearing capacity requirements, but also effectively suppresses void development, reduces corrosion risk, delays structural performance degradation, and improves long-term service reliability. The findings provide a theoretical basis and engineering reference for the durability design and lifecycle performance optimization of prestressed rock anchor foundations for onshore wind power structures in extreme environments. Furthermore, the study underscores the critical role of advanced anti-corrosion coatings and surface protection systems in mitigating the coupled corrosion-degradation mechanisms, aligning with the scope of this Special Issue on corrosion protection and durability of infrastructure in harsh environments. Full article

As mineral resource extraction progressively extends to greater depths, the complex deep underground environment poses severe corrosion-induced deterioration risks to anchoring structures such as rock bolts. Anchorage failure has thus become a critical safety concern constraining the stability of deep roadways. To address the failure mechanisms of anchoring systems under multi-physical field coupling effects, this study conducts numerical simulations of multi-field corrosion processes and ultrasonic nondestructive testing (NDT) based on a numerical modeling platform. The influence of temperature on corrosion rate and current density is systematically analyzed, and interface response characteristics are extracted and interpreted for defects of varying dimensions. A spatial complementary mechanism under different corrosion defect configurations is revealed, and a health diagnosis system incorporating multiple critical indicators is established. The results indicate that elevated temperature significantly accelerates bolt corrosion: the rise in temperature shifts the equilibrium potential negatively and exponentially increases the reaction rate constant, both of which synergistically promote anodic dissolution. In ultrasonic testing, monitoring points along the main axis are positioned within the transmission-focused zone, where defects induce acoustic wave diffraction and superposition such that even minor defects cause a multiplication of the dominant frequency. Lateral monitoring points lie in the reflection–interference zone, where small defects preferentially attenuate energy, while larger defects manifest as amplitude reduction and first-arrival wave lag; all characteristic indices increase monotonically with defect size. Based on the numerical simulation outcomes, a four-level grading diagnosis standard and a “bottom–lateral” detection scheme are proposed as simulation-based reference indicators. The model effectively reproduces both corrosion deterioration and acoustic wave propagation characteristics, thereby providing a quantitative basis for the assessment of anchoring structures in high-temperature deep underground environments. Full article

To improve the surface service durability and heat-transfer performance of brass heat-dissipation components, Ni–graphene (Ni–Gr) composite coatings were prepared on brass substrates by electro-brush plating, and the effects of working voltage on the coating microstructure and overall performance were investigated. The coating thickness ranged from 6.667 to 19.334 μm. The results show that the coating prepared at 7 V had a thickness of 8.524 μm, a dense microstructure, relatively uniform graphene dispersion, and the lowest Raman I_D/I_G ratio of 1.2146, thereby exhibiting the best overall performance. The microhardness of this coating reached 395 HV, which was approximately 190% and 127% higher than those of the brass substrate and pure Ni coating, respectively. Its corrosion current density in 3.5 wt.% NaCl solution decreased to 1.0143 × 10⁻⁵ A/cm², corresponding to a 90.4% reduction relative to the pure Ni coating. The room-temperature thermal conductivity of the coating/brass composite specimen reached 145 W/(m·K), which was 29.5% higher than that of the brass substrate. When the working voltage increased to 9–11 V, although the coatings became thicker, surface nodules coarsened, pores/pinholes increased, and graphene agglomeration intensified, leading to declines in mechanical properties, corrosion resistance, and thermal conductivity. These results demonstrate that an appropriate working voltage is beneficial for coordinating Ni nucleation/growth and graphene co-deposition, and is a key processing parameter for obtaining high-performance Ni–Gr composite coatings for brass heat-dissipation components. Full article

High-frequency ohmic heating (HFOH) represents a significant advancement over conventional ohmic heating (OH) by reducing limitations related to electrode–food interactions. Although conventional OH provides rapid and volumetric heating, its performance is often limited by electrode fouling and corrosion. A key finding of the present review is that the existing literature lacks a unified frequency-based classification of OH, making it difficult to compare processing conditions, interpret frequency-dependent mechanisms, and identify appropriate operating regimes for different food applications. To address this gap, this review proposes a novel functional classification based on the dominant electrical behavior, electrochemical phenomena, and processing characteristics observed across different frequency ranges. Accordingly, this review classifies OH systems into four functional frequency ranges: low-frequency range (<1 kHz); medium-frequency range (1–<10 kHz); high-frequency range (10–30 kHz); and ultra-high-frequency range (>30 kHz–<1 MHz). HFOH operates within these upper ranges to minimize electrochemical reactions at the electrode interface, resulting in faster and more homogeneous temperature distributions. These advantages lead to lower cooking losses and improved retention of nutritional, sensory, and structural attributes, particularly in heterogeneous and multiphase food systems where conventional methods often fail. However, these effects are matrix-dependent, and low-frequency OH can sometimes achieve stronger microbial inactivation via electroporation. Recent research highlights the importance of computational modeling and simulation for process optimization, as these tools enable accurate prediction of thermal profiles and help reduce temperature irregularities. This review analyzes published studies on HFOH and compares its performance with other OH systems. Applications of HFOH across various food processes are evaluated, including microbial and enzyme inactivation, cooking, heating extraction, thawing, tempering and drying/dehydration. Furthermore, this study discusses the benefits and challenges of HFOH and provides strategic recommendations to address these technical limitations, offering insights that may support its future practical implementation and scalability within the modern food processing industry. Full article

The influence of different heat treatment processes on the microstructure and mechanical properties of 18Ni350 maraging steel manufactured by selective laser melting and the corrosion resistance of TiB₂ ceramic coatings Electro-Spark-Deposited on its surface when immersed in high-temperature molten aluminum have been investigated in the present study. The microstructures and mechanical properties of the differently heat-treated samples were analyzed using various precision instruments. The results reveal that the as-built sample exhibits a microstructure composed of cellular and columnar dendritic grains. After solution treatment, the microstructure fully transforms into lath-like martensite. After direct aging treatment, the cellular structures diminish, while precipitates at grain boundaries proliferate with increasing aging temperature. SAT- treatment achieves full microstructural homogenization, featuring fine-lath martensite and a small amount of randomly distributed austenite particles. DA- and SAT- significantly improve the strength, hardness and modulus of samples and were found to reduce the toughness and plasticity. After solution treatment at 800 °C for 1 h followed by aging treatment at 520 °C for 6 h (SAT 800-520), the specimen achieved an UTS of 2476 MPa while maintaining an EL of 4.6%. The TiB₂ coating and the Cr interlayer deposited via ESD form a continuous interfacial bond with the substrate, demonstrating favorable adhesion. After 4 h of static immersion in high-temperature molten aluminum, the coating remains intact without complete delamination, delivering effective protection to the substrate. Full article

Ni–Co γ/γ′-strengthened superalloys are key structural materials for modern energy and flow turbomachinery systems due to their exceptional high-temperature strength, creep resistance, as well as hydrogen and corrosion stability. However, operation in gaseous hydrogen environments typical of hydrogen-cooled generators, cooled gas-turbine blades, and emerging hydrogen-energy technologies can significantly affect their microstructural stability and fracture behavior. This study presents a comprehensive multiscale review of hydrogen-induced nanoscale degradation and crack initiation mechanisms in Ni–Co superalloys produced by wrought, powder metallurgy, and additive manufacturing routes. Transmission electron microscopy combined with quantitative morphometric analysis was employed to characterize the size, morphology, and spatial distribution of γ′ precipitates, revealing a dense population of coherent particles predominantly in the 40–120 nm range, governed by a log-normal distribution. Correlations between precipitate size, aspect ratio, and circularity indicate the onset of partial loss of coherency and coarsening for particles exceeding ~80 nm, creating favorable sites for hydrogen localization. The presence of TCP phases (η, σ, μ, Laves) and carbides at grain boundaries and within grains was shown to enhance microstructural heterogeneity and act as effective hydrogen traps, promoting interfacial decohesion and microcrack initiation. To support microstructural interpretation, convolutional neural network analysis with Grad-CAM visualization was applied to SEM images, enabling the identification of the structural regions most sensitive to hydrogen-assisted damage, particularly γ/γ′ interfaces and defect clusters. The results demonstrate that hydrogen-induced degradation in Ni–Co superalloys is governed by the coupled interactions among microstructure, hydrogen distribution, and local stress state. The findings provide a physically grounded basis for optimizing alloy chemistry, heat treatment, and additive manufacturing parameters, as well as for developing AI-assisted predictive models for the durability of critical components in hydrogen-energy and high-temperature power-generation systems to increase hydrogen safety. Full article

Copper alloying of Ti6Al4V via liquid-phase sintering (LPS) is a promising route to enhance densification and mechanical properties for biomedical implants. This study investigates the effect of sintering temperature (900–1100 °C) on the densification, microstructure, and electrochemical behavior of Ti6Al4V–20 wt.% Cu composites. Samples were fabricated via pressureless sintering, maintaining a constant relative green density of 72.7%. The results show that the relative density increased progressively from 78.6% at 900 °C to 98.1% at 1100 °C. Microstructural analysis revealed a transition from fragmented Ti-Cu dendritic structures to refined globular intermetallic, with enhanced copper diffusion into the α-Ti matrix above 1000 °C, accompanied by the formation of TiCu and Ti₂Cu intermetallic phases. Correspondingly, microhardness increased systematically from 313 HV to 473 HV, correlated with reduced porosity and intermetallic reinforcement. Electrochemical tests in Ringer’s solution indicated that while higher temperatures improve structural integrity, the distribution of Cu-rich phases significantly influences corrosion kinetics. These findings demonstrate that sintering at 1100 °C optimizes the densification–microstructure relationship, providing a technical basis for the development of high-performance Ti-based composites. Based on previous studies of Ti–Cu systems, these materials may exhibit antibacterial activity, although no biological or antibacterial tests were performed in the present work. Full article

The formation of phosphate conversion coatings on St20 low-carbon steel was studied in order to evaluate the effect of organic accelerators on coating formation and protective performance. The influence of pH, temperature, treatment time, and stirring rate on coating formation was studied by gravimetry and SEM-EDS, the influence of accelerators was studied by Raman spectroscopy, salt spray testing, polarization measurements, EIS, and dynamic LPR monitoring. Efficient coating formation was achieved at an initial pH of 3.0, elevated temperature, and intensive stirring; the process showed diffusion-controlled behavior with an apparent activation energy of 28 kJ/mol. Sodium nitrite accelerated coating formation but did not increase the limiting coating mass. Among the organic additives, catechol provided the most pronounced improvement in corrosion resistance, which was attributed to lower effective porosity and possible incorporation of catechol-derived oxidized fragments into the phosphate layer. The catechol-modified coating also improved electrochemical resistance and did not impair the adhesion of subsequent acrylic paint. These results indicate that catechol is a promising organic modifier for zinc phosphate intermediate pretreatment layers. Full article

ZIF-8-modified micro-arc oxidation (MAO) coatings have attracted considerable attention for improving the corrosion resistance of aluminum alloys, owing to their combined barrier and chemical protection effects. In this work, ZIF-8/MAO composite coatings were fabricated via in situ solvothermal growth, and the effects of solvothermal temperature and time on coating evolution and corrosion performance were systematically investigated. The coatings were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results show that increasing the solvothermal temperature promotes ZIF-8 formation, which may be related to enhanced coordination reactions and particle growth. Prolonging the solvothermal time induces a transition from ZnO-dominated coatings at 8 h to ZIF-8-dominated structures at 16–24 h, whereas unconverted ZnO is still detected after prolonged growth. The in situ-grown ZIF-8 particles cover the MAO surface and contribute to the sealing of surface micropores and cracks, forming a more compact composite barrier structure. The reduced coating performance at 220 °C or after 32 h may be associated with excessive particle refinement, local structural imperfections, or reduced coating integrity under prolonged or high-temperature solvothermal conditions. Electrochemical impedance spectroscopy (EIS) results reveal that the composite coating exhibits a charge transfer resistance more than one order of magnitude higher than that of the bare MAO coating, indicating significantly enhanced barrier protection. These findings demonstrate that in situ-grown ZIF-8 is an effective strategy for improving the corrosion resistance of MAO coatings on aluminum alloys. Full article

Efficient melting of direct reduced iron (DRI) is essential for improving the stability and productivity of low-carbon steelmaking processes. In this study, the effect of FeO content on DRI melting behavior and coupled interfacial reactions in slag–refractory systems was investigated. Synthetic slags containing 10, 20, and 28 wt.% FeO were prepared, and hot-state melting experiments, viscosity measurements, FactSage calculations, and SEM/EDS analyses were conducted to clarify the relationship among slag properties, DRI melting, and interfacial evolution. The results showed that increasing FeO content significantly accelerated DRI melting and reduced the overall melting time. This improvement was mainly attributed to the enhanced fluidity and heat-transfer capability of the slag. Temperature-centered Arrhenius fitting showed that the apparent viscous-flow activation energies varied only within a limited range when fitting uncertainties were considered, indicating that the decrease in viscosity with increasing FeO content should not be attributed solely to a reduction in activation energy. Instead, the change in slag fluidity is associated with the combined effects of FeO on melt structure, pre-exponential fitting parameters, and temperature-dependent flow behavior. Meanwhile, the calculated thermal conductivity increased with FeO content, further promoting heat transfer from the molten slag to the DRI surface. Microstructural observations revealed that, under low-FeO conditions, a relatively continuous aluminosilicate-rich reaction layer formed at the DRI–slag interface, which hindered slag penetration and delayed melting. In contrast, high-FeO slag exhibited stronger wettability and penetration ability, allowing slag to infiltrate deeply into the porous DRI structure and form an extensive slag–iron mixed reaction zone. At the slag–MgO refractory interface, FeO promoted Fe²⁺/Mg²⁺ interdiffusion and the formation of a dense magnesiowüstite, (Mg,Fe)O, reaction layer. However, excessive FeO also intensified slag penetration and refractory corrosion. These results demonstrate that FeO plays a dual role in DRI melting systems by enhancing DRI melting efficiency while simultaneously aggravating refractory degradation, highlighting the need to balance melting performance and refractory stability in FeO-containing slag design. Full article

To meet the combined requirements of high strength, intrinsic corrosion protection, and cost effectiveness for bridge cable wires, 316L/SWRH82B stainless-steel/high-carbon-steel clad wire rods were manufactured under industrial hot rolling conditions. Three initial rolling temperatures of 1000, 1024, and 1047 °C were investigated through metallographic observation, quantitative image analysis, EPMA characterization, SEM fractography, and tensile testing, with 15 specimens tested for each temperature group. The EPMA results, together with the metallographic observations, were used to evaluate carbon diffusion, interfacial elemental redistribution, and decarburization. As the initial rolling temperature increased from 1000 to 1024 and 1047 °C, the decarburized-layer thickness on the SWRH82B side increased from 7.42 ± 1.28 µm to 11.31 ± 1.74 µm and 18.15 ± 1.76 µm, respectively, whereas the carburization-affected-zone thickness on the 316L side increased from 48.36 ± 2.73 µm to 63.04 ± 3.06 µm and 68.73 ± 3.65 µm, respectively, demonstrating pronounced asymmetric interfacial reaction–diffusion. The average tensile strengths of the three groups were 1120.07, 1146.27, and 1152.28 MPa, with corresponding standard deviations of 14.83, 4.55, and 13.34 MPa and coefficients of variation of 1.32%, 0.40%, and 1.16%, respectively. Among the tested conditions, the 1024 °C group exhibited the lowest tensile-strength standard deviation and coefficient of variation, indicating the best tensile stability and mechanical consistency. Although the 1047 °C group achieved the highest average tensile strength, it also exhibited reduced cladding thickness uniformity and renewed mechanical scatter. All 45 tensile specimens were fractured on the SWRH82B side without obvious macroscopic interfacial delamination, indicating that the interface was not the preferential macroscopic fracture path under the present uniaxial tensile-loading condition. However, the intrinsic interfacial bonding strength was not directly quantified in this work. Therefore, 1024 °C is identified as the preferred initial rolling temperature for the specific billet geometry and industrial rolling conditions examined in this work, rather than a universally applicable value. The present study is limited to as-hot-rolled clad wire rods; corrosion performance, multi-pass cold drawability, and the final performance of bridge cable wires after drawing remain to be experimentally validated. Full article