Search Results (1,510)

This study presents a comparative investigation of the microstructure, phase composition, microhardness, tribological behavior, and corrosion resistance of heterogeneous coatings deposited on St3 steel by twin-wire electric arc spraying (TWEAS). Three wire combinations were examined: ER309LSi + Steel 70, Sv-08G2S + Steel 70, and 30KhGSA + ER309LSi. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), Vickers microhardness testing, ball-on-disc tribological measurements, and potentiodynamic polarization in 3.5 wt.% NaCl solution. All coatings exhibited a characteristic lamellar structure with a thickness of 340–360 μm and hardness values significantly higher than those of the steel substrate. The 30KhGSA + ER309LSi coating demonstrated the highest cross-sectional microhardness (532 ± 13 HV) and the lowest specific wear rate (0.411 × 10⁻⁴ mm³/(N·m)), which was more than five times lower than that of the substrate. The enhanced wear resistance was associated with the formation of the Cr₇C₃ and Cr₂₃C₆ carbide phases, as identified by XRD. The Sv-08G2S + Steel 70 coating exhibited the lowest corrosion rate among the investigated coatings due to its more homogeneous ferritic structure and reduced electrochemical contrast between lamellae. The results demonstrate that the phase composition and distribution of alloying elements play a decisive role in determining the functional properties of heterogeneous TWEAS coatings. Full article

The use of direct reduced iron (DRI) in electric arc furnace (EAF) steelmaking has grown in popularity, yet dephosphorization, as a special concern because of high phosphorous levels, is yet to be fully understood. Here, a dynamic process model, accounting for phosphorus behavior under the circumstance of a continuous charge of raw materials and semi-continuous flushing slag in an industrial DRI-charged EAF, is developed and verified to predict trajectories of steel and slag phosphorus levels and slag chemistry in real time based on process conditions. The model is then employed to evaluate dephosphorization in a wide range of DRI phosphorus levels and process conditions. It is found that dephosphorization in industrial DRI-charged EAFs does not occur in equilibrium, with the phosphorus partition range of 20~70, compared to 130~170 for equilibrium conditions. For the phosphorus content in DRI, ranging from 0.02 wt.% to 0.2 wt.%, a dephosphorization ratio of more than 81% can be achieved at a slag basicity of 2.3. Dephosphorization is likely easily achieved even at a relatively low slag basicity of 1.5~1.7 when DRI containing phosphorus levels as high as ~0.1 wt.% is used, attaining a dephosphorization ratio of more than 70%. The current model can serve as a valuable tool, providing a knowledge base to assist in the design, operation, and optimization of DRI-charged EAF practices. Full article

In mesoscopic domain energy models of electrical steel sheets, the demagnetizing field H_d is usually held constant at its domain-wall-complete value throughout magnetization. This treatment overestimates the magnetostatic energy at intermediate states and distorts the simulated hysteresis loop. We introduce a field-dependent coefficient υ_H that scales the magnetostatic energy at each field step. The coefficient is calculated from the aligned-domain area measured by magneto-optical Kerr microscopy and is anchored at the negative coercivity point H = −H_c, where the macroscopic magnetization vanishes and the aligned-domain area S₀ is minimal. The definition follows from the linear relation H_d ≈ N_d·M that holds during domain-wall motion. Measurements in two observation zones of a grain-oriented steel give consistent υ_H curves, confirming the repeatability of the method. When the correction is incorporated into an Assembly Domain Structure Model, the coercivity error drops from 113% to 9–22% relative to the experimental average, with the predicted value falling inside the experimental range, and the remanence error drops from 39.9% to 15–17%. The same correction, applied to a second grain-oriented steel of a different grade, likewise reduces the coercivity and remanence errors (to about 23% and 18%, respectively), confirming that the method is applicable across grades. Full article

Steel dust is a waste generated during steelmaking in an electric arc furnace (EAF), which contains a high proportion of iron-bearing compounds, leading to the inclusion of this waste as a resource in the circular economy for steelmaking. In addition to the limitation related to granulation (the waste must be processed to obtain larger particle sizes), a limiting factor is the increasingly high Zn content due to the low-quality ferrous charge. For the recycling of steelmaking dust, preliminary processing is necessary to reduce zinc. The paper presents, in addition to qualitative characterization of steel dust, laboratory experiments on the compositional changes associated with zinc redistribution applying the hydrometallurgical leaching process in an alkaline environment, using sodium hydroxide (NaOH). The changes in the chemical composition were identified and evaluated using X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDX). The experiments consisted of treating steel dust samples with 5 M NaOH at 25, 70, 80 and 90 °C for 60 min, using solid-to-liquid ratios of 10, 15, and 25 g/L. The results indicate a reduction in ZnO content ranging from 4.52% to 16.82%, as determined from Na₂O-free normalization data. Room-temperature samples show only marginal changes in ZnO content. The XRF and EDX analyses indicate a moderate and condition-dependent redistribution of zinc in the solid phase after alkaline treatment, as evaluated using Na₂O-free normalized data. These values are derived exclusively from solid-phase measurements (XRF/EDX) and do not include zinc in the leachate; therefore, true zinc extraction efficiency cannot be determined. The research results attest to the viability and efficiency (as a solid-phase compositional transformation process) using NaOH as a leaching agent for the studied steel dust, thus providing a potential pathway for improved waste recycling in the steel industry. Full article

The choice of brass as the substrate due to its widespread use in soft non-ferrous industrial components such as bearings and electrical connectors creates the primary basis of novelty in this study. While prior tribological studies on titanium aluminum nitride (TiAlN) coatings is primarily focused on hard substrates such as steel and WC–Co, this work addresses the research gap by presenting a systematic investigation of the combined influence of sputtering power and working pressure on TiAlN coatings deposited on brass. Application of TiAlN coatings on brass surfaces was accomplished using magnetron sputtering. Within the scope of this study, the influence of sputtering power and working pressure on the tribological and structural attributes of TiAlN films is evaluated. The analysis of surface morphology is carried out using scanning electron microscopy (SEM), while structural characteristics revealed a progressive increment in the intensity of the (103) and (107) peaks with variation in deposition parameters. An analysis was conducted to evaluate the tribological properties of the TiAlN coating using a pin-on-disk tribometer. The study involved varying the speeds, loads, and sliding lengths. The optimized condition achieved wear reduction as high as 22% compared to uncoated brass at a sliding distance of 785 m, which highlights the strong dependence of wear performance on deposition parameters. The wear rates of TiAlN-coated brass ranged between 1.03 × 10⁻³ and 5.87 × 10⁻⁴ mm³/Nm depending on parameters like load, sliding distance and speed. Conversely, TiAlN-coated brass pins prepared at varying power showed wear rates ranging from 1.83 × 10⁻⁴ to 5.87 × 10⁻⁴ mm³/Nm. These findings demonstrate that optimization of TiAlN coating parameters on brass can significantly enhance wear resistance, which ultimately improves the durability and performance of engineering components in tribological applications. Full article

Copper and its alloys are widely used in electrical, automotive, aerospace, and energy applications because of their excellent thermal and electrical conductivity. However, the low hardness and poor wear resistance of pure Cu limit its use under tribologically demanding sliding conditions. In this study, Cu matrix composites reinforced with 1 wt.% boron carbide (B₄C), boron (B), chromium (Cr), cobalt (Co), alumina (Al₂O₃), and graphite (Gr) were fabricated by powder metallurgy and comparatively evaluated under identical processing and testing conditions. Phase constitution and microstructural characteristics were analyzed by XRD, SEM, and EDS, while mechanical and tribological behavior was assessed by Vickers hardness and dry sliding wear tests. All reinforcements improved the hardness of the Cu matrix compared with unreinforced Cu. The hardness increase followed the order Cu–B₄C (68.91%) > Cu–B (66.43%) > Cu–Gr (63.97%) > Cu–Al₂O₃ (61.79%) > Cu–Cr (42.69%) > Cu–Co (36.04%). Dry sliding wear tests, performed under a 10 N normal load, 0.05 m s⁻¹ sliding speed, and 1000 m sliding distance against a 316L stainless-steel ball, showed that all reinforced composites exhibited lower mass loss and more stable sliding behavior than pure Cu. Among all samples, Cu–B₄C displayed the best wear performance, with a 154.8% improvement in wear resistance relative to pure Cu. SEM analysis of the worn surfaces revealed that reinforcement addition reduced severe plastic deformation, groove formation, and delamination, leading to a more stable wear regime. Graphite- and boron-containing composites benefited from interfacial lubrication and contact stabilization, whereas B₄C and Al₂O₃ improved wear resistance through rigid-particle strengthening and enhanced load-bearing capacity. By comparing ceramic, metalloid, metallic, oxide, and solid-lubricating reinforcements at the same low addition level and under identical processing and testing conditions, this study provides a reinforcement-selection framework for Cu-based composites requiring improved hardness and dry-sliding durability. Full article

Ultra-high-performance concrete (UHPC) is known for its exceptional compressive strength and durability; however, its brittle nature requires fiber reinforcement to improve toughness and tensile performance. This study investigates the synergistic effects of triple fiber reinforcement, including desized and sized carbon fibers (0.2–1.0 vol%), steel fibers (1.0 vol%), and polypropylene fibers (0.2 vol%) on the fresh, mechanical, durability, microstructure, and fire resistance properties of UHPC. The experimental program included workability, compressive and flexural strength, load-deflection behavior, electrical resistivity, dynamic modulus of elasticity, SEM analysis, and fire resistance at elevated temperatures (425 and 900 °C). The results showed that desized carbon fibers performed better than sized fibers by improving workability, fiber dispersion, flexural behavior, and fiber–matrix bonding. The optimal triple-fiber composition, DC1.0P0.2S1.0, achieved the highest flexural strength of 24 MPa while maintaining compressive strength above 141 MPa. The triple-fiber system provided effective multi-scale crack control, where PP fibers prevented explosive spalling, carbon fibers bridged meso-crack control, and steel fibers enhanced macro-crack load transfer and ductility. SEM analysis further confirmed better dispersion and stronger interfacial bonding of desized carbon fibers. Overall, the optimized triple-fiber system significantly improved flexural performance, toughness, workability, and fire resistance without notably reducing compressive strength, demonstrating strong potential for advanced structural applications. Full article

The irradiation-induced precipitation of Mn-Ni-rich precipitates (MNPs) or Mn-Ni-Si-rich precipitates (MNSPs) is the primary cause of embrittlement in reactor pressure vessel (RPV) steels. In this study, high-precision electrical resistivity (ER) measurements (10 nΩ·m accuracy) were employed to probe the thermal stability of aging-induced MNSPs in RPV model steels that were aged at 600 °C for 30 h. We report the discovery of oscillatory precipitation and re-dissolution of MNPs/MNSPs, evidenced by alternating ER peaks upon repeated thermal cycling to 950 °C. This oscillatory behavior is further confirmed by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) observations. Internal friction (IF) results indicate that the oscillatory precipitation and re-dissolution of MNPs/MNSPs should occur predominantly within the grain interiors rather than at grain boundaries (GBs). Full article

In the Arabian Gulf region, saltwater desalination is considered to be a significant process in producing clean water. This paper presents a sustainable, combined process for upgrading a Doha reverse osmosis (RO) plant in Kuwait. A pilot-scale microbial desalination cell (MDC) stack is proposed as a pre-treatment unit prior to the RO process in order to improve plant performance. A cost–benefit analysis is conducted for the combined system to emphasize the significance of the MDC–RO process. In RO, the expected energy consumption is 2.6–13 kWh per m³ of desalinated water, whereas using MDC can reduce this to about 0.52–5.3 kWh/m³. Moreover, this new technology using catalytic MDCs can help in improving electric current production and reducing the amount of rejected brine and membrane fouling in the RO process. The electric current is improved by reducing MDCs’ internal resistance using a reduced graphene oxide/polyaniline composite-coated stainless steel mesh cathode electrode. Layer-by-layer electro-deposition can be applied to achieve these coatings. An intermediate zeolite filter is proposed to mitigate RO membrane fouling. The combined system’s natural zeolite-membrane filter improves water purification. In this study, we assessed the combined MDC–RO process for upgrading the Doha plant’s performance in terms of quality, cost, and time. The suggested catalytic MDC, using efficient, low-cost materials as cathode electrodes with an equivalent daily cost of 0.01 USD/m³ and a desalination efficiency of about 40%, acts as an alternative to high-cost platinum metal electrodes. The results also indicate that the equivalent daily cost of energy consumption using the MDC process is about 0.03 USD/m³, whereas the investment cost is about 0.4 USD/m³ daily for one year of cell operation. Full article

In hybrid rolling bearings operating under extreme high-temperature and high-load conditions, steel rolling elements are prone to early failure, which has accelerated the widespread adoption of ceramic materials. To address the limitations of conventional studies, which have focused mainly on macroscopic wear parameters while neglecting subsurface failure mechanisms and the relationship among sintering process, microstructure, and fatigue performance, this work systematically compares the tribological behavior of Si₃N₄ ceramic balls fabricated by high-pressure electric resistance hot-pressing (REHP) and B₄C ceramic balls prepared by conventional hot pressing (HP) against 52100 steel counterparts. The central innovation of this study lies in clarifying, based on Hertzian contact theory and Lundberg-Palmgren life theory, that subsurface orthogonal shear stress, rather than surface compressive stress, is the fundamental driving force for contact fatigue failure of ceramic balls. In addition, two distinct damage evolution modes are revealed: B₄C exhibits early-stage brittle fracture and large-scale spalling, whereas REHP-Si₃N₄ is characterized by microcrack initiation and slow crack propagation. Moreover, the intrinsic mechanism by which the REHP process significantly enhances the contact fatigue life of ceramics is elucidated; namely, it refines grain size, eliminates residual porosity, and increases densification. The results show that, under the same high-load conditions, the mass loss of REHP-Si₃N₄ ceramic balls is only 35.7% of that of HP-B₄C, while the service life is extended by 20%. This work provides a key theoretical basis for ceramic material selection and sintering process optimization in high-performance hybrid bearings. Full article

The article deals with non-destructive methodologies for assessing and preventing corrosion of polymer-coated underground pipelines, advanced corrosion-barrier coating systems based on extruded three-layer high-density polyethylene (3LPE), corrosion control strategies for buried oil, gas, and water transmission infrastructures, and mechanisms and engineering approaches for corrosion prevention and mitigation. The quality assurance of newly polymer-coated underground pipelines, following construction (installation and backfilling), is vital for evaluating the polymer coating quality state and the efficiency of passive anti-corrosion protection, aimed at reducing corrosion risks and prolonging the pipeline’s service life. The evaluation relies on the coating average specific electrical resistance and the presence of coating defects (number, total area, and distribution) of inspected pipeline sections. In this study, based on extensive real data obtained from testing of newly installed underground water and oil/gas pipeline networks (60 projects with a total pipeline length of 260 km) with various technical characteristics, Drainage Test and DCVG (Direct Current Voltage Gradient) complementary non-destructive indirect methods have been investigated to determine the quality level and identify the location and severity of defects in polyolefin (polyethylene) coatings. The novel concepts and criteria were defined: the quantitative criteria for average specific electrical resistance are established; in addition, a new parameter related to the specific coating defects ratio is introduced, which has been shown to correlate with the criteria for the average specific electrical resistance of the polymer coating and consumed electrical current; finally, following DCVG measurements of the 3LPE coating system, a novel degree of relative defect sizes (%IR) for repairs has been suggested. The innovative and comprehensive approach can support the efforts of regulatory quality assurance, design, maintenance, safety, and research communities to ensure the long-term integrity and sustainability of underground polymer-coated steel pipelines. Full article

The contact performance of automotive airbag electrical connectors directly affects the stable conduction of the initiator circuit, yet sufficient failure data are difficult to obtain for such long-life safety-critical components. This study develops a degradation model for connectors with stainless-steel pins, beryllium-bronze sockets, and Ni/Au composite coatings, using the contact resistance increment as the degradation measure. Considering the accumulation of oxidation corrosion products under thermal stress, as well as the local film rupture and re-oxidation induced by fretting wear under combined temperature-vibration stress, a nonlinear time scale t^α is introduced to describe the nonlinear growth of contact resistance. A random-drift nonlinear Wiener process is then constructed: the diffusion term represents local fluctuations within each sample trajectory, while the random drift rate captures growth-rate differences among samples. Parameter estimation was performed using degradation data obtained from 160 °C high-temperature and 160 °C temperature-vibration accelerated degradation tests. The estimation results show that the stress-class-specific time-scale model better reflects the different degradation mechanisms than a common time-scale model, and that the temperature-vibration group exhibits higher resistance growth and stronger trajectory fluctuations. Model diagnostics support the description of the main increment distribution and sample-to-sample differences, while EDS and XPS results provide supplementary evidence for oxidation-related surface composition changes and coating-state evolution. Full article

As a clean and renewable energy source, wind energy offers lower development and utilization costs than solar energy, making it the most promising renewable option. However, the carbon footprint of offshore wind power and its external impacts on cross-regional carbon emissions have not been investigated sufficiently. Using the provinces of Guangdong and Jiangsu as case studies, this study employs socioeconomic and environmental statistical data. It applies the environmentally extended multi-regional input–output (EE-MRIO) method to quantify cross-regional environmental spillover effects associated with offshore wind power development. The findings show that China’s power structure has been continuously optimized, with offshore winds achieving leapfrog growth since 2010. Through a “local consumption” model, offshore wind power in Guangdong and Jiangsu has effectively replaced coal-fired generation, substantially reducing carbon emissions locally and in neighboring areas. Jiangsu has reduced CO₂ emissions by 16.72 million tons annually, and Guangdong by about 7.23 million tons annually. Furthermore, offshore wind development drives the green transformation of upstream industries (e.g., steel, non-ferrous metals, and chemicals). It extends carbon-reduction benefits to resource-rich regions such as the Northwest and North China. As major manufacturing hubs, both provinces lowered the embodied carbon intensity of their export products by using clean electricity, thereby indirectly reducing the national carbon footprint through cross-regional trade. This study offers scientific insights to help policymakers optimize offshore wind layouts, facilitate coordinated regional emission reductions, and advance sustainable energy transitions. Full article

The article presents the results of experimental studies on the possibility of predicting the efficiency of CO₂ mineralization using metallurgical wastes (MWs) from the perspective of chemical thermodynamics and on identifying, accordingly, promising MWs for the production of construction materials and products. The study examined MWs from major Russian iron and steel producers, namely: blast furnace, electric steelmaking, ferroalloy, converter steelmaking slag, as well as nepheline slag, a by-product of nepheline ore processing for alumina. The CO₂ binding capacity of MWs was determined using experimental samples fabricated by semi-dry pressing of MW powders, followed by curing them in a gas atmosphere with an CO₂ concentration of 80% vol. It was found that the investigated MWs are capable of absorbing and binding CO₂, thereby improving their physical and mechanical properties. Experimental samples made from nepheline slag bind 11.3 to 12.0 wt.% of CO₂; samples from steelmaking slags: up to 9 wt.% or more; and samples from blast furnace dump slag: approximately 5.5 wt.% At the same time, the compressive strength of samples from steelmaking slags exceeds 100 MPa, that of samples from nepheline slag approaches 80 MPa, and that of samples from blast furnace dump slag exceeds 50 MPa. It has been established that predicting the efficiency of CO₂ mineralization by metallurgical wastes based solely on chemical thermodynamics is not entirely accurate. To develop a preliminary forecasting model for the carbonate hardening potential of various MWs, further studies are needed to identify additional key factors influencing the carbonate hardening process of MWs. Full article

Ultra-high-performance concrete (UHPC) formulated with alternative binders represents a promising pathway for reducing carbon emissions while enabling multifunctional material performance. This study investigates the mechanical and electrical evolution of two systems: a traditional Portland cement-based UHPC (REF) and a geopolymer counterpart (GEO) where cement is fully replaced by ground granulated blast furnace slag (GGBS) and silica fume. By evaluating both mixes with and without steel fibers, the research assesses how binder chemistry interacts with conductive pathways to influence strength, resistivity, and impedance. Mechanical testing revealed comparable 28-day compressive strengths for the reference and geopolymer mixes (123 MPa and 120 MPa, respectively), which increased to 139 MPa and 130 MPa upon fiber incorporation. Electrical characterization showed that the geopolymer binder significantly enhances conductivity; resistivity values dropped from 9645 Ω·m in the reference mix to 925 Ω·m in the geopolymer and further to 76 Ω·m with fiber reinforcement. Impedance spectroscopy supported these results, as the GEO mixes displayed smaller Nyquist arcs compared to the REF system, indicating greater ionic mobility associated with pore solution chemistry and the GGBS-rich gel structure. Ultimately, this study demonstrates that geopolymer UHPC matches the mechanical integrity of Portland-based systems while offering superior electrical conductivity, making it a strong candidate for low-carbon, self-sensing infrastructure. Full article