Search Results (4,412)

Abrasive Water Jet Machining (AWJM) is increasingly used for post-weld surface modification of dissimilar metallic joints; however, the depth-dependent surface response of welded stainless–carbon steel joints remains insufficiently quantified. In this study, four dissimilar welded systems, TIG 316, TIG 309, ARC 316, and ARC 309, were systematically investigated to elucidate the combined influence of welding technology, filler composition, and jet parameters on surface integrity. Surface roughness was evaluated at multiple jet-penetration depths using amplitude (R_a, R_q, R_t, R_z) and statistical (R_sk, R_ku) descriptors. The results reveal three distinct hydrodynamic erosion regimes governing texture evolution. Duplex welds (TIG 309 and ARC 309) exhibited highly stable erosion behavior, with R_a confined to 1.91–2.99 µm, low roughness gradients (ΔR_a/Δdepth = 0.012–0.015 µm·mm⁻¹), and near-Gaussian surface statistics (R_sk ≈ 0, R_ku ≈ 3–4). In contrast, austenitic welds (TIG 316 and ARC 316) showed pronounced depth-dependent instability, with R_a increasing up to 4.54 µm and the normalized roughness ratio R_z/R_a reaching 5.69 in TIG 316 near the jet exit. Strong inter-parameter correlations in duplex welds (r ≥ 0.94) confirm uniform erosion kinetics, whereas weakened correlations in austenitic systems (r ≈ 0.70–0.83) reflect jet-energy dissipation. These findings establish a mechanistically grounded AWJM performance window for achieving R_a ≤ 3 µm in dissimilar welded steels. Full article

:This study assessed the effects of groundwater interacting with aggregate produced from steel slag, used as a ballast material in a waterproofing system protecting the road surface under high groundwater table conditions. Field investigations were carried out, with hydrochemical analyses of groundwater and water draining through the structure, mineralogical characterisation of the slag, and geochemical modelling using the PHREEQC programme with inverse modelling. The results showed that water flow through the slag aggregate caused strong alkalisation of the solution and changes in the concentrations of Ca, Mg, Na, Cl, sulphates and carbonate components. Inverse modelling enabled the identification of eight acceptable mass balance models. The main primary phases involved in the transformations were larnite, merwinite, mayenite, halite and, locally, slag glass. Their dissolution contributed Ca, Mg, Al, Si, Na and Cl to the solution. The increases in Na and Cl concentrations were interpreted primarily as the result of an external influx of road salt, rather than as an intrinsic property of the slag. The secondary products were dominated by amorphous silica, calcite, ettringite and brucite, indicating silica removal, carbonation, sulphate fixation and the partial immobilisation of Mg. The results confirm that slag aggregate remains geochemically active in contact with groundwater; however, simultaneous carbonation and secondary mineralisation favour the gradual stabilisation of the water–slag system. Full article

The microstructures and torsional fracture morphologies of S2 alloy steel screwdriver bits were characterized by scanning electron microscopy (SEM). The bits were oil-quenched from 830 °C and 860 °C and subsequently tempered at 150 °C and 170 °C under three carbon potential levels (0.35, 0.40, and 0.45). In parallel, Deform-3D and Ansys Workbench were employed to simulate and compare the microstructure evolution during quenching, the residual stress field after quenching and tempering, and the stress distribution developed under torsional loading. The results reveal that the non-planar fracture and low qualification rate of the bits arise from two independent but synergistic mechanisms: (1) insufficient austenitizing at 830 °C fails to produce fully uniform austenite, resulting in non-uniform martensitic microstructure and inhomogeneous hardness distribution after quenching; (2) low furnace carbon potential (≤0.35) causes surface decarburization and the formation of massive ferrite at the near-surface region, which acts as preferential crack initiation sites. Furthermore, the transformation stress generated during quenching, the residual stress remaining after tempering, and the stress concentration at tooth edges under service loading jointly promote crack initiation and propagation. A uniform, high-hardness tempered martensite microstructure is obtained when the bits are austenitized at 860 °C with the carbon potential strictly maintained between 0.40 and 0.45, held for 60 min before oil quenching, and air-cooled after tempering at 170 °C. This optimized heat-treatment route eliminates surface decarburization, ensures microstructural homogeneity, reduces residual stress, and enables the bits to fail by planar fracture under torsional load with 100% qualification rate. Full article

Recently, gel coatings have been studied as a promising method that can provide electrochemical corrosion protection. This review presents a comprehensive analysis of advanced gels such as sol–gel coatings, hybrid organic–inorganic, self-healing, and crack repair gels. These gels employ different mechanisms for corrosion protection, from passive barrier formation to active self-healing and corrosion inhibition. Their performance can be influenced by gel chemistry, microstructure, and the incorporation of functional additives. Recent studies have shown that gel coatings can achieve promising corrosion resistance. This high efficiency can be attributed to the formation of dense barrier layers that restrict the mobility of attacking ions. The incorporation of functional additives such as silica nanoparticles can enhance mechanical characteristics for gels. In the field of crack-repair, bio-gels based on microbially induced calcium carbonate precipitation show acceptable sealing capability. Additionally, the evolution of polarization resistance and corrosion current suggests the sustained protective performance of these gels. Multifunctional gels extend this concept by combining crack sealing, alkalinity restoration, and steel re-passivation. Gel coatings are transitioning from simple barrier coatings to multifunctional smart inhibition capable of self-healing, corrosion sensing, and long-term durability. This review highlights the relationship between gel chemistry, microstructure, and corrosion resistance for the development of next-generation gel coatings. Full article

This study examines the evolution of microstructure, the metastability of retained austenite (RA), and the corresponding mechanical behavior exhibited by a nanostructured bainitic bearing steel subjected to prolonged austempering within a transformation stasis regime. The results indicate that following the completion of nanostructured bainitic formation at 300 °C for 3 h, a prolonged austempering time does not alter the microstructure, but reduces the dislocation density in BF while increasing the carbon content in RA. For the 4 h and 6 h specimens, a reduction in the overall RA mechanical stability is observed, accompanied by different transformation rates of stress-induced martensite during tensile deformation. This behavior is largely due to the weakened constraint effect of the BF matrix and the evolution of a carbon concentration gradient within the RA. During the transformation stasis, prolonged austempering elevates the yield strength while maintaining an unchanged ultimate tensile strength, albeit with a marginal reduction in microhardness. Relative to the baseline elongation recorded for the 3 h specimen, both the 4 h and 6 h specimens exhibit enhanced ductility, with the 4 h specimen yielding a peak value of 16.8%, which is 1.66 times that of the 3 h specimen. This improvement stems largely from the greater RA volume fraction that transforms into stress-induced martensite in the 4 h specimen, as well as its continuous and stable transformation rate during tensile deformation. Therefore, it can be concluded that an appropriately prolonged austempering time within nanostructured bainitic transformation stasis is essential for optimizing mechanical performance. This study provides a low-cost, energy-saving isothermal heat treatment technical scheme for mass industrial production of high-performance bearing steel. Full article

As pollution reduction, carbon mitigation, and the green transition of energy-intensive industries accelerate worldwide, how pollution emission performance is formed in the steel industry remains insufficiently understood. Unlike previous studies that regard pollution emission performance as a single environmental outcome, this study develops a three-dimensional framework integrating industrial development, environmental performance, and socio-economic performance (IES). To address this gap, we combine comprehensive evaluation, coupling coordination analysis, and obstacle diagnosis to assess the pollution emission performance of China’s listed steel companies from 2019 to 2024. The results show that: (1) the overall pollution emission performance of the steel industry continued to improve, with significant increases in the industrial level and environmental benefit subsystems, whereas the socio-economic subsystem declined continuously after 2021 and dropped to 0.461 in 2024, becoming a key bottleneck constraining overall improvement. (2) The coupling coordination degree among the IES subsystems generally increased, but differences among enterprises remained, indicating that the green transition of listed steel companies did not progress synchronously. (3) The obstacle degree results indicate that environmental constraints were relatively prominent in the early stage of the study period, the industrial dimension generated periodic pressure around 2021, and the relative contribution of the socio-economic dimension increased during 2022–2024. These findings provide empirical evidence for evaluating pollution emission performance, identifying key weaknesses, and designing differentiated management strategies for listed steel companies in China. Full article

The corrosion-protection performance of zinc oxide-hybrid polymeric coatings is traditionally attributed to the individual contributions of their constituent phases. This study reveals that the calcination temperature of zinc oxide (ZnO) filler is a critical, previously overlooked processing parameter that dictates not only filler crystallinity but also the collective synergistic failure mechanism of the entire coating system. Herein, we demonstrate that incorporating ZnO calcined at 500 °C yields a ternary chitosan–graphene oxide–zinc oxide/epoxy (CS–GO–ZnO/EP) composite coating with a highly compact, dense morphology, minimal internal porosity, and exceptional filler dispersion, as validated by FTIR, XRD, and SEM analyses. The optimized CS–GO–ZnO/EP coating applied to carbon steel exhibits outstanding dry and wet pull-off adhesion strengths, the highest surface hydrophobicity (102.2°), and superior electrochemical barrier protection. Notably, after a 120-h immersion period in an aggressive 3.5 wt.% NaCl electrolyte, the CS–GO–ZnO/EP (500 °C) maintains excellent coating resistance (R_coat = 1.06 × 10⁵ Ω) and a minimized corrosion rate (CR = 0.074 mm/y). This thermal threshold is a key processing window that improves chemical bonding and compatibility between the different parts of the hybrid matrix without causing the severe nanoparticle sintering, phase aggregation, and micro-cracking that happen at 650 °C. This work offers a significant advancement in the design of eco-friendly, high-performance hybrid coatings, demonstrating that precise control of the inorganic phase’s thermal history provides a direct pathway toward superior durability, hydrophobicity, and electrochemical stability for carbon steel protection in aggressive marine environments. Full article

To clarify the origin of asymmetric arc ablation in hydroelectric generator slip rings, a Steel 45/carbon current-carrying friction pair was selected to investigate the influence of current polarity on arc behaviour and interfacial damage. Static gap discharge tests (10 A) and dynamic tests (current density of 10 A/cm², sliding velocity of 0.419 m/s) were performed to characterize polarity-dependent erosion behaviour. The results indicate that, under the steel(+)–carbon(−) condition, the arc exhibits unstable burst-like discharge accompanied by intense spark spattering. The carbon cathode experiences severe material loss due to the combined effects of cathode-spot heating, positive-ion bombardment, and molten metal droplet impact. The steel surface is characterized by nested erosion pits and spherical resolidified spatter particles, while the apparent ablation-affected area shows an overall increase with accumulated arc duration, with a more pronounced expansion observed at longer durations. Pronounced bidirectional material migration and interfacial elemental enrichment are observed under the steel(+)–carbon(−) configuration, resulting in an apparent net mass loss rate approximately 2.5 times higher than that under the steel(-)–carbon(+) configuration. The reversed steel(−)–carbon(+) configuration produces a spatially constrained and stable arc discharge, accompanied by a continuous remelted layer and network-like thermal-stress cracks on the steel surface. Polarity reversal changes the direction of the interfacial electric field and charged-particle migration, thereby regulating cathode electron emission, arc discharge behaviour, energy distribution in the near-electrode region, and bidirectional material migration across the interface. These results provide a theoretical basis for elucidating the polarity-dependent arc ablation mechanism of steel/carbon friction pairs and for optimizing polarity configuration and differentiated protection strategies for hydroelectric generator slip rings. Full article

This study investigates the efficiency of green corrosion inhibitors derived from spent coffee grounds (SCGs) for OL 37 carbon steel in 0.5 M H₂SO₄ and 1 M HCl environments. The aqueous extracts, labeled K1 and K2, were obtained through specialized extraction techniques and characterized by HPLC. Their protective performance was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). FT-IR spectroscopy and SEM-EDX analysis confirmed the presence of a protective inhibitor film on the OL 37 surface, attributed to the adsorption of organic molecules from the SCGs extract (K1 and K2). The adsorption behavior followed the Langmuir isotherm, with high adsorption constants and standard free energy values (ΔG°_ads), indicating a mixed-mode adsorption mechanism. Furthermore, the negative Gibbs free energy values of adsorption confirm the spontaneity of the adsorption process. Thermodynamic studies conducted between 293 K and 333 K demonstrated the temperature dependence of the inhibition process. Results showed that at a concentration of 800 ppm and 1000 ppm, both inhibitors exhibited high efficiency, reaching 96% for K1 and 95% for K2. Full article

Tool steel TD salt-bath vanadizing generally relies on expensive analytical-grade raw materials, yet systematic investigations into low-cost industrial borax-based vanadizing of 9SiCr steel remain insufficient. This work intends to optimize the industrial salt-bath vanadizing process and clarify the growth mechanism of vanadium carbide coatings. TD thermal diffusion vanadizing was performed on 9SiCr steel using a molten borax salt bath containing industrial-grade borax and V₂O₅. Metallurgical microscopy, XRD, SEM-EDS and microhardness testing were adopted to systematically explore the effects of treatment temperature and holding time on coating thickness, microstructure and hardness. Continuous, dense VC coatings with favorable metallurgical bonding were fabricated. Coating thickness increased linearly with temperature and followed a parabolic growth law with respect to holding time. The optimized parameter was identified as 970 °C for 4 h, yielding a 8.3 μm thick coating with an average microhardness of ~2500 HV and an 8 μm thick diffusion transition layer. Comparative chromizing experiments indicated that the chromium carbide coating (16.7 μm) was approximately twice the thickness of the VC coating under identical conditions, demonstrating that VC coating growth is restricted by the diffusion supply of active carbon from the substrate. This research provides experimental data and theoretical guidance for the industrialized optimization of TD salt-bath vanadizing for 9SiCr steel. Full article

The growing demand for natural aggregates and continued stockpiling of steel slag have increased interest in using steel slag aggregate (SSA) in road engineering. However, delayed hydration of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO), porous and rough surfaces, and the potential release of hazardous elements constrain its long-term application. This review compares aging treatment, surface modification, direct carbonation, microbially induced calcium carbonate precipitation (MICP), and combined treatments from a raw-material heterogeneity and defect-oriented perspective. Their effectiveness is strongly condition-dependent. Aging treatment can control volume expansion, but reaction depth and treatment uniformity remain limited. Surface modification can reduce water absorption and improve interfacial performance but cannot eliminate internal expansive phases. Direct carbonation and MICP can stabilize reactive phases, refine pore structures, and reduce the mobility of some elements, but are limited by mass transfer and equipment requirements, and by mineralization uniformity and ammonium by-product management, respectively. Combined treatments can address multiple defects but increase process complexity, resource consumption, and quality-control requirements. Because material properties and evaluation methods vary among studies, reported performance gains should not be directly used for technology ranking. Instead, technology selection should follow the framework of “raw-material characteristics–dominant defects–preferred technology–engineering boundaries”. From a life-cycle perspective, sustainability depends on balancing resource and environmental benefits against additional treatment burdens. Near-term implementation should integrate raw-material classification, process monitoring, long-term durability and dynamic leaching verification, and the progressive incorporation of key performance and environmental indicators into road-material specifications and engineering acceptance criteria. Full article

Corrosion in carbon steel piping systems is a critical issue in hydroelectric power plants, as progressive wall thickness loss may compromise integrity and operational reliability. This study proposes a data-driven framework combining descriptive statistical analysis and distinct clustering methods to map and rank corrosion conditions in water pipeline systems of a hydroelectric power plant in Brazil. A total of 4916 pipe segments from 20 generators (generating units 1 and 2) were evaluated and the feature matrix included wall loss descriptors, measured thickness statistics, minimum allowable thickness, wall integrity indicators, pipe geometry, segment type, and system information. Descriptive analyses revealed heterogeneous corrosion patterns across generating units, segment types, diameters, and inspection points, with localized severe wall loss conditions in specific segments. A principal components analysis was applied to reduce the original feature space while preserving approximately 80% of the cumulative variance, as suggested by the literature. The best clustering solution was obtained using a weighted consensus model based on the Calinski–Harabasz index, resulting in five degradation/integrity profiles that support segment-level corrosion ranking and inspection prioritization. The proposed framework provides a structured basis for integrating inspection data, statistical descriptors, and integrity indicators into maintenance and decision support processes for hydroelectric power plant piping systems. Full article

Driven by global carbon neutrality targets, the low-carbon transformation of power systems necessitates rigorous carbon evaluation of grid infrastructure. However, existing assessments of overhead transmission lines often exhibit incomplete life-cycle boundaries and lack a coordinated approach to subjective and objective weight allocation. To address these gaps, this study targets overhead transmission lines and constructs a comprehensive low-carbon evaluation index system comprising 14 indicators across four life-cycle stages, namely design, construction, operation, and recycling. A hybrid evaluation model is proposed based on the combined analytic hierarchy process and entropy weighting method. The analytic hierarchy process is utilized to derive expert-based subjective weights, while the entropy weighting method extracts objective data variations from multiple samples, which are then integrated to obtain robust composite weights. An empirical analysis conducted on a 500 kV double-circuit overhead transmission line project in China validates the proposed framework. The results reveal a comprehensive evaluation score of 80.219, corresponding to a “low-carbon” grade. Moreover, the line loss rate (0.234227), operational carbon emissions (0.133978), and steel consumption per unit length (0.122381) are identified as the pivotal indicators dominating the evaluation outcome. This research provides quantitative support and practical criteria for decision-making regarding low-carbon design, green construction, operational loss reduction, and resource-oriented retirement of transmission line projects. Full article

High-carbon martensitic steels for bearing components are conventionally low-temperature tempered for stress relief, yet the influence of tempering temperature on compressive and fatigue wear resistance remains unclear, directly affecting the service life of bearing races and rollers. In this study, a high-carbon martensitic steel was tempered at 170 °C, 200 °C, and 230 °C. The microstructural evolution, compressive properties, and contact fatigue wear resistance were systematically investigated, along with the corresponding strengthening and wear mechanisms. After spheroidizing annealing and quenching, the microstructure consists of high-carbon martensite and retained austenite, with a high density of dislocations and fine twins. Tempering decomposes retained austenite into tempered martensite and promotes fine carbide precipitation, processes that become more pronounced at higher temperatures. Consequently, hardness decreases from 810 HV in the as-quenched state to 690 HV after 230 °C tempering, while compressive failure strain increases from 10.5% to 24.1%. More importantly, under cyclic contact stress, the 230 °C-tempered specimen exhibits approximately 33% lower wear mass loss than the 170 °C-tempered counterpart, despite its lower hardness. This unexpected improvement is attributed to the formation of a distinct plastic deformation zone in the near-surface region, which absorbs greater strain energy and delays fatigue spallation. The well-tempered martensitic matrix accommodates more long-range dislocation slip, enabling a transition from fatigue spallation to a more ductile failure mode. These findings provide new insights into the role of low-temperature tempering in balancing strength, ductility, and wear resistance, and offer practical guidance for optimizing heat treatment protocols to enhance the contact fatigue performance of bearing steels. Full article

To investigate the application potential of ultrafine composite powder (UCP) as a novel supplementary cementitious material to replace ground granulated blast-furnace slag (GBFS) in cement-based materials and its underlying mechanism, this study first compared the activity differences between UCP and GBFS and their effects on mortar workability. Subsequently, multiple characterization techniques including XRF, XRD, TG/DTG, FTIR, mapping, SEM-EDS, and BET were employed to systematically examine the morphology, composition, particle size distribution, and pore structure characteristics of the two powders. Results show that UCP exhibits slightly higher 3 d and 28 d strength activity indices than GBFS, but contributes less to strength progression between 3 and 28 days. In terms of chemical composition, UCP contains lower combined CaO + MgO + Al₂O₃ content but significantly higher C and Fe levels and alkalinity than GBFS. Phase and microstructural analyses further reveal that UCP is predominantly composed of GBFS, fly ash (FA), steel slag, limestone powder, gypsum, superplasticizer, and alkaline activator, and is characterized as a mesoporous material with pores arising from fragmented FA, unburned carbon residues, and grinding-induced cracks. Quantitatively, the BET specific surface area, Blaine specific surface area, and total pore volume of UCP are 2.47, 1.59, and 3.31 times those of GBFS, respectively. Therefore, the early-age activity advantage of UCP is mainly attributed to the filling effect, the additional nucleation sites provided by its larger specific surface area, and the chemical activation induced by alkali and gypsum. Full article