Search Results (153)

Given the multi-basin raw material base for coking that has been formed at most industry enterprises, there is an urgent need to optimize the component composition and improve the basic technological methods of coal raw material preparation, taking into account the petrographic characteristics of coal batches. A comprehensive study of the components included in a coke chemical enterprise’s coking raw material base was carried out. The work used standardized methods for studying coal and coal batches’ technological and plastic–viscous properties. The qualitative characteristics of coke were determined using physical–mechanical and thermochemical methods of studying standardized indicators: crushability (M₂₅), abrasion (M₁₀), reactivity (CRI), post-reaction strength (CSR), and specific electrical resistance (ρ). The results were analyzed using the licensed Microsoft Excel computer program. Based on the results of proximate, plastometric, and petrographic analyses of the studied coal samples and data from experimental industrial coking, proposals were made to optimize the component composition, properties of the coal batch, and technology for its preparation for coking. The established inverse dependence of Gibbs free energy (ΔG_f,total) on the reaction capacity of coke CRI and its direct reliance on its post-reaction strength CSR confirmed the feasibility of using ΔG_f,total as a thermodynamic predictive parameter for optimizing and compiling coal batches that produce less reactive, stronger coke. This made it possible to improve the quality indicators of metallurgical coke. Thus, according to the M₂₅ crushability index, the mechanical strength increased by 0.6%, and the M₁₀ abrasion decreased by 0.4%. Significant improvements in thermochemical properties and an increase in the orderliness of the carbon structure were recorded: the CRI reactivity decreased by 3.1%, the CSR post-reaction strength increased by 8.3%, and the specific resistance decreased by 8.4%. Full article

The aim of this study is to evaluate the effect of various lubrication systems (dry cutting, MQL, and nano-MQL) on the machinability of AISI 1040 medium-carbon steel. By dispersing titanium carbide (TiC) nanoparticles into environmentally friendly sunflower oil, a new type of nano-MQL fluid was developed. Machinability parameters such as surface finish, cutting force, energy consumption, chip structure, and tool degradation were examined through scanning electron microscopy (SEM). Based on experimental observations, the use of the nano-MQL technique led to a notable enhancement in machining performance when compared to both dry and traditional MQL machining. In addition, surface roughness was substantially reduced with the nano-MQL, suggesting more effective lubrication and cooling. Reductions in cutting forces and energy consumption were also observed, indicating more efficient material removal and lower mechanical resistance. The SEM examination of the cutting tools proved the low wear rate of the nano-MQL, which exhibited less adhesion and more abrasion wear, and of dry cutting, which showed the most serious wear. Furthermore, chip morphology illustrations indicated that the chips of nano-MQL were relatively uniform and segmented, indicating superior chip breaking quality and cutting stability. The results suggest that employing TiC nanoparticles in MQL offers a clear enhancement of cutting performance in terms of process efficiency, surface quality, and tool wear. These results validate the capability of nano-MQL as an environmentally friendly and high-performance lubrication method for turning medium-carbon steels, supporting more sustainable and efficient manufacturing operations. Full article

This study examines advanced electrospark alloying (ESA) as a pulse-driven surface hardening technique for marine engineering components operating in corrosive and abrasive environments. Coatings were deposited using cobalt-based (Stellite 6), nickel-based (NiCrBSi), titanium-based (VT1-0), and boron-based (B₄C) electrodes, with pulse energies of 0.2–0.5 J, discharge frequencies of 100–200 Hz, electrode feed rates of 5–8 mm/min, applied loads of 15–20 N, and treatment durations of 40–60 s. The effects of processing parameters on coating microstructure, adhesion strength, microhardness, corrosion resistance, and wear behaviour were systematically evaluated. ESA treatments increased microhardness by 35–48% and adhesion strength by 22–30%, while reducing the corrosion rate from 0.043 mm/year to 0.025–0.027 mm/year and lowering wear volume loss by 40–47%. Compared with high-velocity oxy-fuel (HVOF) spraying and laser hardening, ESA achieved 37–58% lower energy consumption and 40–70% lower CO₂ emissions. These findings highlight ESA as an energy-efficient and environmentally sustainable option for on-site maintenance and modernisation of maritime equipment. Full article

Ice accretion on critical transportation infrastructure presents serious operational risks and economic challenges, highlighting the need for sustainable anti-icing solutions. This study develops a strong PDMS-based composite coating on aluminum by incorporating carbon nanotubes (CNTs) and carbon powder, effectively merging passive superhydrophobicity with photothermal capabilities. We systematically assess how different ratios of CNTs to carbon powder (3:1, 1:1, 1:3) influence surface morphology, wettability, anti-icing performance, mechanical durability, and corrosion resistance. The morphological analysis shows the formation of hierarchical micro/nano-structures, with the optimal 1:3 ratio (designated as P13) resulting in dense, porous agglomerates of intertwined CNTs and carbon powder. P13 demonstrates high-performing superhydrophobicity, with a contact angle of 139.7° and a sliding angle of 9.4°, alongside a significantly extended freezing delay of 180 s at −20 °C. This performance is attributed to reduced water–surface interaction and inhibited ice nucleation. Mechanical abrasion tests indicate remarkable durability, as P13 retains a contact angle of 132.5° and consistent anti-icing properties after enduring 100 abrasion cycles. Electrochemical analysis reveals exceptional corrosion resistance, particularly for P13, which achieves a notable 99.66% corrosion inhibition efficiency by creating a highly tortuous diffusion barrier that protects against corrosive agents. This multifunctional coating effectively utilizes the photothermal properties of CNTs, the affordability of carbon powder, the low surface energy of PDMS, and the thermal conductivity of aluminum, presenting a robust and high-performance solution for anti-icing applications in challenging environments. Full article

The Qinghai–Tibet Plateau presents a unique challenge for infrastructure development due to its extreme geological and climatic conditions—high elevation, large diurnal temperature fluctuations, frequent freeze–thaw cycles, intense ultraviolet radiation, and seasonal precipitation. These factors greatly accelerate the weathering of rock materials, leading to aggregates with increased porosity, microcracking, and weakened mechanical properties. While the engineering implications of such degradation are evident, the underlying material science of weathered aggregates—particularly their microstructure–property relationships—remains insufficiently explored, necessitating further investigation to inform material selection and design. In this study, three representative types of weathered aggregates (silica-rich, carbonaceous, and alumina-rich), alongside unweathered natural aggregates, were examined through both macro-scale (density, water absorption, crushing value, abrasion resistance) and micro-scale (scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS)) analyses. To capture the material evolution, we introduced a simplified classification framework based on the Si/Al ratio and porosity and applied a gray entropy correlation model to quantify the coupling between microstructure and mechanical performance. Results show that weathering reduces the Si/Al ratio from 2.45 to 1.82, increases porosity from 4.2% to 12.7%, enlarges the average pore size to 0.85 μm, raises microcrack density to 1.40 μm/μm², and increases the proportion of connected pores to 68.2%. These microstructural degradations correlate with decreased aggregate density, increased water absorption (up to 8.0%), higher crushing value (27.4%), and abrasion resistance loss (26.0%). Based on these findings, a weathered aggregate classification and pretreatment strategy is proposed, offering a practical reference for engineers to improve material performance in high-altitude road construction. Full article

Tribological processes in extreme environments pose serious material challenges, requiring coatings that resist both wear and corrosion. This review summarizes recent advances in protective coatings engineered for extreme environments such as high temperatures, chemically aggressive media, and high-pressure and abrasive domains, as well as cryogenic and space applications. A comprehensive overview of promising coating materials is provided, including ceramic-based coatings, metallic and alloy coatings, and polymer and composite systems, as well as nanostructured and multilayered architectures. These materials are deployed using advanced coating technologies such as thermal spraying (plasma spray, high-velocity oxygen fuel (HVOF), and cold spray), chemical and physical vapor deposition (CVD and PVD), electrochemical methods (electrodeposition), additive manufacturing, and in situ coating approaches. Key degradation mechanisms such as adhesive and abrasive wear, oxidation, hot corrosion, stress corrosion cracking, and tribocorrosion are examined with coating performance. The review also explores application-specific needs in aerospace, marine, energy, biomedical, and mining sectors operating in aggressive physiological environments. Emerging trends in the field are highlighted, including self-healing and smart coatings, environmentally friendly coating technologies, functionally graded and nanostructured coatings, and the integration of machine learning in coating design and optimization. Finally, the review addresses broader considerations such as scalability, cost-effectiveness, long-term durability, maintenance requirements, and environmental regulations. This comprehensive analysis aims to synthesize current knowledge while identifying future directions for innovation in protective coatings for extreme environments. Full article

The wear failure of vertical shaft planetary mixer blades under complex working conditions directly affects the quality and productivity of concrete. Given that it is time-consuming and labor-intensive to obtain the wear characteristics of mixer blades by experimental methods, this study used numerical simulation to analyze the effects of different factors on the wear characteristics of mixer blades based on the Hertz–Mindlin with JKR cohesive contact model and the Archard wear model. The results of this study show that under the influence of different factors, the blade is subjected to tangential cumulative contact energy and contact force is significantly larger than that in the normal direction, the wear of the blade is judged to be the form of abrasive wear accompanied by impacts, and the wear on the outer middle and lower edge regions of the blade is the most serious. Specifically, for every 5 rpm increase in mixing speed, the blade wear rate increases by 24.14% on average; for every 5° increase in blade angle, the blade wear rate decreases by 2.9% on average; for every 10% increase in the mass ratio of stone aggregate, the blade wear rate increases by 5.95% on average; conical aggregates have the most serious effect on blade wear, while spherical aggregates have the most minor effect. This study provides the theoretical basis and numerical support for understanding the reasons for blade wear loss and enhancing the service life of mixer blades. Full article

Metallic glasses (MGs) with excellent mechanical properties have significant applications in frontier technological fields such as medical, energy and aerospace industries. Recently, MGs have been considered as ideal candidates for subzero engineering applications due to their disordered atomic structure array. However, the mechanical properties and wear behaviors of MGs at subzero temperatures have rarely been explored. In this work, the wear properties and wear mechanisms of Zr-based MG were systematically evaluated at a subzero temperature of −50 °C. Compared to the wear results at room temperature, MG in a subzero environment shows a ~60% reduction in wear rate. The main contributing factor is that MG at room temperature will easily forms a thin, brittle oxide layer at the sliding interface, which will lead to oxidation, adhesive and abrasive wear on its surface, whereas these wear behaviors do not occur in subzero conditions where only abrasive wear occurs. Meanwhile, MG at subzero temperatures has a higher elastic modulus. These properties make MG more wear-resistant in subzero environments. The current study will provide new perspectives on the wear mechanisms and subsurface deformation of MG in subzero environments and valuable insights into the use of MG in subzero engineering applications, such as deep space and polar exploration. Full article

The inherent flammability and hydrophilicity of nylon/cotton (NC) blend fabrics limit their practical applications. Traditional hydrophobic treatments often involve fluorinated compounds or nanomaterials, which raise environmental concerns and exhibit poor durability. To address these issues, this study developed a sustainable multifunctional finishing strategy. Initially, the nylon/cotton blended fabric was pretreated with 3-glycidyloxypropyltrimethoxy silane (GPTMS). An intumescent flame retardant coating based on bio-derived phytic acid (PA) and polyethyleneimine (PEI) was constructed on NC fabrics via a layer-by-layer (LBL) self-assembly process. Subsequently, polydimethylsiloxane (PDMS) was grafted to reduce surface energy, imparting synergistic flame retardancy and superhydrophobicity. The treated fabric (C-3) showed excellent flame retardant and self-extinguishing behavior, with no afterflame or afterglow during vertical burning and a char length of only 35 mm. Thermogravimetric analysis revealed a residual char rate of 43.9%, far exceeding that of untreated fabric (8.6%). After PDMS modification, the fabric reached a water contact angle of 157.8°, indicating superior superhydrophobic and self-cleaning properties. Durability tests showed that the fabric maintained its flame retardancy (no afterflame or afterglow) and superhydrophobicity (WCA > 150°) after 360 cm of abrasion and five laundering cycles. This fluorine-free, nanoparticle-free, and environmentally friendly approach offers a promising route for developing multifunctional NC fabrics for applications in firefighting clothing and self-cleaning textiles. Full article

Laser-boronized parts manufactured by a selective laser melting process from 18Ni to 300 maraging steel are investigated in this study. Two main issues are addressed, namely (i) the possibility to restore the hardness of the heat-affected zone (HAZ) formed during laser processing and (ii) the effect of re-aging on the hardness and wear resistance of the laser-boronized layer with a hypoeutectic structure. Optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, microhardness measurements, the “ball-on-plate” dry sliding test, and the two-body dry abrasive wear test were employed to answer the questions. The results confirmed that HAZ is formed with the dissolution of intermetallides formed before and undergo full (near the molten pool) or partial (at some distance from the molten pool) iron–base matrix recrystallization. The hardness of HAZ (350–550 HK0.05) has been restored after re-aging to the 550–600 HK0.05 level. Moreover, a certain positive effect of re-aging on the laser-boronized layer with a hardness of ~470–750 HK0.2 is established, associated with structural transformations induced by aging in the iron-based solid solution phase. The hardness increased by ~9–25%. The wear resistance of the hardest boronized samples (~750 HK0.2) under dry sliding and dry abrasive wear conditions was ~5.8 times and 3.7 times higher than that of the aged control sample, while re-aging provided further improvement of these characteristics. The presented results provide insights into the effectiveness of laser-boronized layers having a hypoeutectic structure in terms of increasing the wear resistance of maraging steel. Full article

Enhancing the durability and tribological performance of babbitt alloys is critical for high-stress applications in automotive, marine, and industrial machinery. The present study explores the electrodeposition of chromium coatings on SnSb11Cu6 alloys to improve their microstructural, mechanical, and tribological properties. The coatings were applied through an electrolytic process and systematically characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy to evaluate their morphology, composition, and wear performance. The chromium coating exhibited a uniform thickness of 20.2 µm and significantly improved the surface hardness to 715.2 HV, far surpassing the matrix and intermetallic phases of the uncoated alloy. Tribological testing under dry sliding conditions demonstrated a 44% reduction in the coefficient of friction (COF) and a 54% decrease in mass wear for the coated alloy, highlighting the protective role of the chromium layer against abrasive and adhesive wear. To further analyze the frictional behavior, a deep learning model based on a one-dimensional convolutional neural network was employed to predict COF trends over time, achieving excellent accuracy with R² values of 0.9971 for validation and 0.9968 for testing. Feature importance analysis identified coating hardness as the most critical factor influencing COF and wear resistance, followed by matrix hardness near the coating. These findings underscore the effectiveness of chromium coatings in mitigating wear damage and improving the operational lifespan of SnSb11Cu6 alloys in high-stress applications. This study not only advances the understanding of chromium coatings for babbitt materials but also demonstrates the potential of machine learning in optimizing tribological performance. Full article

In the process of herringbone gear grinding, excessive grinding force leads to a large increase in grinding specific energy. A large increase in the specific grinding energy can easily lead to an increase in the transient cutting load. It leads to grinding burn, tooth surface crack and other undesirable phenomena, which ultimately affect the surface quality and service performance of the workpiece. This paper is based on the contact mechanics of workpiece materials. The number of dynamic effective abrasive particles is considered. Combined with the mechanism of grinding force, the model is developed. Based on the consideration of the wear characteristics of the grinding wheel and the structure parameters of the gear itself, the grinding force model was modified. The accuracy of grinding force model is improved by dividing the effective contact angle of grinding grains into four cases. The experimental results show that the normal grinding force error reaches 10.73% and the tangential grinding force error reaches 10.34%. The model reveals the grinding mechanism, optimizes grinding parameters and improves grinding efficiency. It provides a new way for high-precision machining of aerospace precision herringbone gear. Full article

The urban heat island effect raises road surface temperatures, increasing energy demands and accelerating pavement deterioration. This study evaluates a polymer-based pavement system using methyl methacrylate (MMA) resin with aluminum silicate (AS), glass bubbles (GBs), and microencapsulated n-docosane phase-change material (PCM) to identify the most effective solution. Indoor laboratory tests determined AS as the optimal choice, balancing thermal insulation, workability, and mechanical strength. AS-containing mixtures reduced surface temperatures by ~10 °C and exhibited superior compressive strength (28.2 MPa at 6 wt%) compared to GB (23.7 MPa at 4 wt%) and PCM (27.2 MPa at 6 wt%). AS also maintained stable viscosity at ≤10 wt%, unlike GB and PCM, which became unworkable above 5 wt%. The AS-based system achieved high skid resistance (90.2 BPN), abrasion resistance (0.1% wear after 500,000 cycles), and low VOC emissions (69.64 g/L). Adjusting the resin-to-BPO ratio to 1:0.42 enabled a 30 min curing time at 25 °C, ensuring practical application. These findings highlight AS as the most effective filler for large-scale deployment. Future work should assess long-term durability and optimize formulations for broader adoption in heat-mitigating infrastructure. Full article

Hardfacing is a welding-related technique aimed at depositing a harder and tougher layer onto a softer, less wear-resistant substrate or base metal. This process enhances the abrasion resistance of the component, increasing its durability under working conditions. A key feature of hardfacing is dilution, which refers to the mixing of the hardfacing layer and the base metal. In this study, shielded metal arc welding (SMAW) was employed to hardface structural steel using chromium carbide vanadium consumables, with results compared to AISI D2 cold-work tool steel. Four different SMAW parameters were tested, and the abrasive test was conducted against SiC discs. Wear rate, represented by the wear loss rate, was correlated to microstructure, scanning electron microscopy, energy-dispersive X-ray spectroscopy, hardness, microhardness, and surface roughness. The results showed that key SMAW parameters, such as welding speed and current, significantly influence wear resistance. Specifically, slower welding speeds and higher currents, which result in greater heat input, led to the increased wear resistance of the deposited layer through the mechanism of the inoculation of larger and harder carbides. Full article

The ultrasonic vibration laser cladding method is a material-saving and green method to fabricate super abrasive structured grinding wheels. However, the mechanism of the ultrasonic vibration’s effect on the movement behavior of abrasive grains in the laser cladding process has not been clarified. To address this, the impacts of ultrasonic vibration on the abrasive grain distribution and movement behavior were experimentally studied, and the numerical simulation method was introduced to simulate the ultrasonic vibration laser cladding process. A two-dimensional Gaussian cross-section heat source model was developed, and its energy density conformed to a Gaussian distribution in both space and time. The simulations of the temperature and fluid fields of the melt pool were carried out. The CBN abrasive grains in the melt pool were subjected to gravity, the buoyancy force, the drag force of the metal fluid, and the sonophoretic radiation force of the ultrasonic vibration. Based on them, the effects of ultrasonic vibration on the movement behaviors and trajectories of the CBN abrasive grains were analyzed. The influence of the ultrasonic amplitude on the distribution of abrasive grains was studied. The simulation results revealed that the abrasive grains could be uniformly distributed on the surface of the cladding layer during the ultrasonic vibration laser cladding process. Full article