Search Results (302)

Although 45 steel is widely used in the manufacture of mechanical parts, its application in harsh working conditions is limited owing to its low hardness, poor wear resistance, and corrosion resistance. Laser cladding can enhance the performance of the working surface without sacrificing substrate toughness. CoCuNiTi HEACs with different cBN additions were successfully prepared on a 45-steel substrate. The phase structure, microstructure, elemental composition, wear, and corrosion behavior of CoCuNiTi + x cBN (x = 0.0, 0.5, and 1.0 wt.%) HEACs were investigated using XRD, OM, SEM, EDS, friction and wear tester, and electrochemical workstation, respectively. The results show that all three coatings exhibit a dual-phase structure composed of FCC and BCC phases. The addition of cBN transforms the alloy phase structure from the original FCC main phase to the BCC main phase. The incorporation of cBN significantly reduces the lattice constant and cell volume of the alloy phase. The change in the alloy phase density is negatively correlated with the cell volume. CoCuNiTi + x cBN (x = 0.0, 0.5, and 1.0 wt.%) alloys have a dendritic structure. No pores were observed in the cBN-containing sample. The content of Ti in the primary phase is the highest. Co is enriched in the dendrite region, and Cu is enriched in the interdendrite region. The significant reduction in the average segregation coefficient for cBN-containing samples is attributed to the heterogeneous nucleation of the alloy melt at lower undercooling levels and the significant increase in the diffusion rate. The friction coefficient of the alloy decreases significantly with increasing cBN content. The sample with 1.0 wt.% cBN shows the best wear resistance, mainly due to the combined effects of hard particle support, solid solution strengthening, phase interface reduction, and high thermal conductivity of cBN. The sample with 1.0 wt.% cBN has the largest capacitive arc radius and charge-transfer resistance, along with the lowest annual corrosion rate, indicating optimal corrosion resistance. This is primarily related to the reduction in pore defects caused by cBN addition, hindrance of uniform penetration of the corrosive medium by dispersed cBN particles, and increased complexity of the anodic dissolution process. CoCuNiTi HEACs reinforced by cBN can simultaneously improve the wear and corrosion resistance of the surface of the 45-steel substrate, providing a feasible strategy for the design of high-performance protective coatings. Full article

The combination of elevated temperature and tribo-corrosion leads to the accelerated degradation of structural components used in many extreme environments. Recently developed high-entropy alloys (HEAs) with multiple principal elements have the potential for superior degradation resistance compared with presently used structural alloys. Here, we demonstrate the microstructural stability, pitting resistance, and superior tribo-corrosion degradation resistance of the AlCoCrFeNi_2.1 eutectic HEA in comparison with duplex stainless steel 2205 in deionized water (controlled low-ionic-strength electrolyte) at 25 °C, 50 °C and 100 °C. The AlCoCrFeNi_2.1 HEA showed excellent microstructural stability and tribo-corrosion resistance at all three temperatures, an order-of-magnitude lower wear rate, and a lower coefficient of friction compared with duplex 2205 steel. The lowest wear volume loss and wear rate for both AlCoCrFeNi_2.1 and duplex steel were recorded at 50 °C, which was attributed to temperature-assisted passivation and formation of a comparatively stable tribological surface condition. These results suggest superior performance of eutectic HEAs in tribo-corrosion applications compared with currently used dual-phase steels and motivate future evaluation in ion-containing industrial water chemistries. Full article

In the automotive industry, the most critical factor affecting dimensional stability during the forming of Advanced High-Strength Steels (AHSSs) is the springback phenomenon. This study systematically investigates the springback behavior of four distinct dual-phase steel grades (DP450, DP600, DP800, and DP1000) in U-shaped body-in-white (BIW) structures across 180 distinct scenarios. The experimental design varied sheet thicknesses (1.2, 1.6, 2 mm), die clearance angles (5°, 10°, 15°), and bending radii (R6, R8, R10, R12, R14). Numerical simulations using Autoform R8 were validated against Atos 3D optical scanning data, achieving values exceeding 0.90 for all grades. Quantitative validation metrics showed exceptional fidelity for lower-strength grades with error margins below 1.1%, while the maximum deviation was limited to 3.1% for the ultra-high-strength DP1000 grade. The findings demonstrate that while increasing material strength substantially intensifies springback, the strategic augmentation of sheet thickness and optimization of die radius effectively mitigate these deviations, thereby enhancing process stability. Full article

Life cycle greenhouse gas (GHG) accounting is increasingly required to substantiate the climate value of wind power beyond “zero-emission” operation, especially under China’s dual-carbon targets. Robust estimation of life cycle GHG emission intensity and the identification of actionable mitigation levers are therefore important for credible transition planning. In this study, a process-based life cycle assessment (LCA) was conducted for a representative 100 MW onshore wind farm in Gaoyou, Jiangsu Province, China, following ISO 14040/14044. To enhance engineering relevance, the construction and installation phase was modeled in a refined manner by decomposing it into road, wind-turbine, booster-station, and transmission-line engineering and further into unit processes. The results show that the overall life cycle GHG emission intensity of the studied wind farm is 24.6 g CO₂-eq/kWh. Scenario analysis further indicates that reducing curtailment and improving end-of-life recycling are effective pathways to lower emission intensity, while the net advantage of hybrid versus steel towers depends on recycling performance when end-of-life credits are included. The study also summarizes practical implications for low-carbon equipment/material procurement and green supply-chain governance, low-carbon construction and logistics, coordinated “source–grid–load–storage” planning to curb curtailment, and more standardized and comparable life cycle carbon accounting for wind projects in China. Full article

In this study, Sn and Ni powders were incorporated into the flux core of brass brazing filler metals, with alloying achieved via in situ synthesis during brazing. The effects of Sn/Ni single and composite additions on the microstructure, melting characteristics, wettability on Q235 steel, and tensile strength of corresponding brazed joints were systematically investigated. Sn addition increased the β-phase fraction, reduced the solidus temperature, and significantly improved wettability—with a maximum unit spreading area of 4.22 mm²/mg at 20 wt.% Sn (2.85 times that of the Sn/Ni-free baseline). However, coarse β-phase grains and their transformation to brittle β′-phase at room temperature resulted in no enhancement of joint tensile strength. Ni addition expanded the α-phase region, refined grains, and induced solid solution strengthening of the α-phase matrix; joint tensile strength peaked at 501 MPa at 20 wt.% Ni (65% higher than the baseline). Excessive Ni (≥40 wt.%) deteriorated wettability due to reduced molten superheat, and 50 wt.% Ni caused α-phase over-strengthening and embrittlement, leading to a sharp strength drop to 214 MPa. The composite addition of 3 wt.% Sn + 10 wt.% Ni reconstructed the filler metal into a refined, uniform grid-like (α + β) dual-phase structure without new phase formation, realizing synergistic optimization of wettability and mechanical properties. The co-added sample exhibited optimal performance, with a unit spreading area of 4.51 mm²/mg and joint tensile strength of 584 MPa (206% and 93% higher than the baseline, respectively). This improvement was attributed to the coupling of uniform stress dispersion by the grid-like microstructure and dual-element functional complementation (Sn for wettability and β-phase strengthening; Ni for grain refinement and α-phase strengthening). This work provides a feasible alloying modification strategy for brass flux-cored brazing filler metals, and the revealed microstructure-performance regulation mechanism offers a valuable reference for developing high-performance brass brazing filler metals. Full article

In the current numerical simulation study of high-strength steel welding, ignoring the phase transformation plasticity effect in the coupling analysis led to a significant deviation between the simulated value of residual stress and the experimentally measured value. To investigate the influence mechanism of the Welding Residual Stresses (WRSs) of 30MnCrNiMo armor steel, the transformation plasticity (TP) coefficient (7.81 × 10⁻⁵ MPa⁻¹) was measured via a Gleeble 3500, and a Finite Element Model (FEM) of thermal–metallurgical–mechanical coupling considering yield strength, volumetric strain and TP behavior in Solid-State Phase Transformation (SSPT) was developed. The results show that the volume expansion during the SSPT is the main factor for the shift in WRS from tensile to compressive. In contrast, the TP effect reduces the peak longitudinal tensile stress in the Heat-Affected Zone (HAZ) by 51 MPa. It also ultimately neutralizes the compressive component in this region. When the martensite fraction ranges from 0.12 to 0.45, transformation plastic strain becomes the dominant factor, leading to a characteristic evolution of longitudinal stress that initially decreases and subsequently increases. The FEM incorporating the TP effect successfully captures the dual reversals of residual stress in the HAZ. The average relative error between the simulated longitudinal stress and the experimental data obtained via X-ray diffraction (cosα method) is 8.8%. The TP coefficient database and the developed multi-field coupling model markedly enhance the predictive accuracy for WRS in 30MnCrNiMo steel, offering a robust theoretical foundation for the design of stress corrosion resistance and the service life assessment of welded joints in armored vehicles. Full article

(WMoTaNb)SiN refractory high-entropy nitride films were deposited via magnetron cosputtering, and the Si content was systematically regulated by varying the Si target power to investigate its influence on the microstructure, mechanical properties, oxidation resistance, and oxyhydrogen-flame ablation behavior. All the films exhibited dense columnar architectures with a distinct FCC + BCC dual-phase structure, whereas increasing the Si target power led to a gradual increase in the deposition rate and Si incorporation. The mechanical properties displayed a non-monotonic relationship with the Si target power, with film applied at an intermediate level of Si target power showing the highest hardness, approximately 28.5 GPa, and improved elastic recovery. Tribological evaluations using a GCr15 steel ball revealed that this film exhibited the lowest wear rate of 4.1 × 10⁻⁶ mm³·N⁻¹·m⁻¹ and a narrower wear track, which was attributed to reduced plastic deformation and the development of an oxygen-enriched tribofilm during sliding. High-temperature oxidation at 1000 °C in air revealed that Si incorporation significantly modified oxide-scale evolution by refining the oxidation products and altering the scale architecture, while the protection of the scale was governed by its continuity and compactness rather than its thickness alone. Oxyhydrogen-flame ablation tests revealed that the degradation behavior was primarily driven by the competition between oxidation-induced mass increase and ablation-induced material loss, with localized film disruption and substrate exposure playing a decisive role. In summary, the findings illustrate that an optimal Si target power establishes a favorable equilibrium between mechanical strength, tribological efficiency, oxidation resistance, and ablation performance, underscoring the potential of (WMoTaNb)SiN films for protective applications in complex mechanical and extreme thermal environments. Full article

CoCuNiTi HEACs reinforced by different diamond contents were prepared on the surface of 45 steel substrate by laser cladding. Their phase composition, microstructure, elemental composition, and wear/corrosion resistance were investigated using XRD, OM, SEM, EDS, a friction and wear testing machine, and an electrochemical workstation, respectively. The results show that after adding diamond, the phase composition of the sample transforms from the original dual-phase structure of the FCC main phase and BCC to the dual-phase structure of the BCC main phase and FCC. With an increase in the diamond content, the diffraction peak intensity of the alloy phases first increases and then decreases. This behavior is related to the significant enhancement of the alloy phase crystallinity with low diamond addition and the intensified crystal lattice distortion caused by excessive diamond addition. The CoCuNiTi + x Diamond (C) (x = 0, 0.5, and 1.0 wt.%) high-entropy alloys have a dendritic structure. After the addition of diamond, no hole defects were observed in the microstructure, and the dendritic structure was significantly refined. Ti and C are enriched in the primary phase, Cu is enriched in the interdendrite regions, and Co exhibits the highest concentration in the dendrite regions. The segregation coefficients of Ni in all three alloys are relatively small. As the diamond content increases, the friction coefficient of the samples decreases significantly. The 1 wt.% diamond sample exhibits the best wear resistance, primarily owing to the combined effects of superhard phase strengthening, solid solution strengthening, and fine grain strengthening resulting from diamond addition. The sample with 0.5 wt.% diamond addition has the lowest self-corrosion current density, highest polarization resistance, and lowest annual corrosion rate, indicating the best corrosion resistance. This performance is mainly attributed to the refinement of the microstructure, reduction in defects, and formation of a dense passivation film caused by the addition of a small amount of diamond. Full article

Molybdenum (Mo) finds extensive applications in the steel industry, and the recycling of secondary molybdenum resources is crucial for the green development of the molybdenum sector. Meanwhile, the large-scale stockpiling of copper slag, a bulk industrial solid waste, poses severe environmental and resource-related challenges. Addressing the common issues of the refractory nature of waste molybdenum disilicide (MoSi₂) and the underutilization of iron resources in copper slag, this study proposes a synergistic smelting approach using copper slag and waste MoSi₂, aiming to realize the coordinated treatment of these two solid wastes and the simultaneous, efficient recovery of valuable metals (Mo and Fe). Under non-isothermal conditions, this work elucidates the phase evolution of copper slag and the decomposition–reduction behavior of MoSi₂; clarifies the dual role of coke as the primary reductant at the initial reaction stage and as a maintainer of a reducing atmosphere during smelting; and systematically investigates the effects of smelting temperature, slag basicity, and coke dosage on metal recovery. The results demonstrate that, under optimized process conditions, the recovery efficiencies of molybdenum and iron can reach 98.97% and 98.46%, respectively. This study provides a new strategy for the enrichment and extraction of metallic elements from waste MoSi₂ and copper slag. Full article

High-entropy alloys (HEAs) represent one of the most promising emerging material families, particularly for advanced surface engineering applications. In this work, a near-high-entropy alloy (near-HEA) coating was produced on a 316L stainless steel substrate using laser metal deposition (LMD) from a powder mixture of Inconel 625, Cr and Mo, without the intentional addition of Fe. Due to dilution from the substrate, the resulting alloy contained elevated Fe content while maintaining Cr, Ni and Mo concentrations within the generally accepted compositional range of HEAs. The deposited layer exhibited a dual-phase microstructure consisting of a face-centered cubic (FCC) phase and a highly distorted tetragonal phase forming a periodic network with a characteristic length scale of several hundred nanometers. The hardness of the coating increased to approximately three times that of the substrate, reaching values of 600–700 HV. To further modify the surface properties, laser-induced periodic surface structures (LIPSS) were generated on the polished coating using femtosecond pulsed laser irradiation at different energy densities. The morphology and subsurface structure of the resulting periodic patterns were investigated by scanning electron microscopy. LIPSS with characteristic dimensions ranging from the micrometer to nanometer scale were successfully produced. Cross-sectional analyses revealed that the underlying dual-phase microstructure remained continuous within the laser-structured regions, indicating that LIPSS formation occurred predominantly via metallic ablation without significant phase transformation or amorphization. These results demonstrate the combined applicability of LMD and femtosecond laser structuring for producing mechanically enhanced, micro- and nanostructured near-HEA coatings with potential for advanced surface-related functionalities. Full article

This study investigates the synergistic effects of an electropulsing (EP) and ultrasonic impact treatment (UIT) hybrid process on the mechanical and corrosion properties of D36 low-carbon steel. Conventional UIT has been shown to enhance surface hardness and induce compressive residual stress but is limited by a shallow affected depth and potential for increased surface roughness, which can exacerbate corrosion. In this work, we integrate high-energy electropulsing with UIT to overcome these limitations. The EP-UIT process leverages the combined effects of acoustoplasticity, thermal softening, and electroplasticity to achieve a significantly deeper hardened layer, extending beyond 2 mm, which is an order of magnitude thicker than that obtained by UIT alone. Microstructural analysis reveals that the process induces continuous dynamic recrystallization (CDRX), resulting in a gradient nanostructured layer with equiaxed grains near the surface and submicron ferrite grains at greater depths. Additionally, cementite dissolution and reprecipitation lead to a dual-phase microstructure comprising a supersaturated ferrite matrix and spheroidized Fe₃C particles. The EP-UIT treatment also forms a dense oxide scale composed primarily of magnetite (Fe₃O₄) and hematite (α-Fe₂O₃), significantly enhancing corrosion resistance. Potentiodynamic polarization tests demonstrate that EP-UIT reduces the corrosion current density by 68% compared to UIT-treated samples, while electrochemical impedance spectroscopy confirms the improved barrier properties of the oxide layer. This innovative approach offers a promising strategy for significantly extending the service life of welded marine structures by concurrently enhancing their mechanical properties and corrosion resistance. Full article

18CrNiMo7-6 steel is widely used in high-load mechanical components, but its poor surface hardness and corrosion resistance limit its service life. This study performed vacuum solid boriding treatment on 18CrNiMo7-6 steel at 1000 °C for different times and investigated the phase composition, microstructure, hardness, surface morphology, and corrosion resistance of the resulting boride layers. The experimental results showed that the boriding treatment formed a dual-phase boride layer on the steel surface, consisting of an outer FeB layer and an inner Fe₂B layer, both of which increased in thickness with increasing boriding time. The surface hardness was significantly enhanced due to the formation of hard boride phases, exhibiting a gradient distribution that correlates with the microstructural transition from the surface to the substrate. The surface roughness exhibited a progressive increase with boriding time, which was attributed to the volumetric expansion and nodular growth associated with boride formation. Furthermore, the corrosion resistance was remarkably improved after boriding and was further enhanced with longer processing times. This improvement is attributed to the thickening and enhanced continuity of the boride layer over time, which mitigated the potential adverse effects of surface roughness. This study demonstrates that vacuum high-temperature boriding effectively co-enhances the surface hardness and corrosion resistance of alloy steel, providing a viable surface modification strategy for high-load components. Full article

Super duplex stainless steels (SDSS) are materials known for their exceptional mechanical strength and high resistance to corrosion due to their dual- phase microstructure consisting of ferrite and austenite in roughly equal proportions. However, the Gas Tungsten Arc Welding (GTAW) process used to join SDSS often causes microstructural imbalances, mainly ferritic structures, or the formation of harmful intermetallic phases, which can weaken the material’ s desirable properties. This study examines the effect of substrate preheating on the microstructure, mechanical properties, and corrosion resistance of UNS S32750 SDSS welds produced by GTAW. Preheating the substrate was considered as a strategy to improve phase balance in the fusion zone by extending the time within the ferrite- to- austenite transformation temperature range, thus slowing the cooling rates. Four conditions were tested: welding at room temperature (RT) and preheating to 100 °C (T100), 200 °C (T200), and 300 °C (T300). Welding parameters remained constant. The fusion zone microstructure was analyzed using metallographic techniques, while mechanical properties were evaluated through microhardness tests. Corrosion resistance was assessed with potential dynamic polarization in a 3.5% NaCl solution. The results showed significant improvements in microstructural balance with higher preheating temperatures. The austenite volume fraction in the fusion zone increased from about 16% at RT to 42% at T 300. Mechanical testing indicated a decrease in microhardness from 341 HV at RT to 314 HV at T 300, reflecting the increased austenite content and its associated toughness. Corrosion tests demonstrated enhanced resistance under preheated conditions, with T 300 exhibiting the highest corrosion potential and the lowest corrosion current, nearing the performance of the base metal. These findings suggest that preheating is a practical, cost- effective method for optimizing the GTAW process for SDSS, eliminating the need for expensive filler materials and stabilizing the microstructure elements. Full article

A semi-analytical mixed-control model based on the Non-Partitioned Local Equilibrium (NPLE) assumption was developed to simulate the austenite phase transformation kinetics during heating and isothermal processes. The model was validated by comparing the simulation results with experimental data, showing excellent agreement. The effects of various model parameters and process conditions on the phase transformation kinetics was investigated. The results indicate that higher heating rates lead to an increase in the austenite volume fraction at the start of the isothermal hold, accelerating the transformation and resulting in a more complete phase transformation. The transformation during the isothermal stage was found to follow a mixed control mode at all investigated heating rates. Increasing the mobility coefficient enhances interface migration, thereby accelerating the transformation kinetics, while decreasing the grain size promotes nucleation, further accelerating the phase transformation. Modifying the diffusion coefficient had a minor effect on transformation kinetics. Additionally, raising the isothermal temperature increased both the austenite volume fraction at the beginning and end of the isothermal process and the interface migration velocity, suggesting that temperature dominates the phase transformation rather than time. The phase transformation mode under different process conditions was also investigated. For both 5 °C/s and 100 °C/s heating rates, the phase transformation during the isothermal process was predominantly interface-controlled, as indicated by the mixed-mode parameter approaching 1, with a rapid increase followed by a decrease. Full article

Dual-phase (DP) steels are widely used in automotive structures due to their excellent strength–ductility balance. This study examines how silicon content and continuous annealing parameters affect the microstructure, mechanical properties, and hydrogen embrittlement (HE) behavior of DP1500 steel. Two steels, 05DP (0.5% Si) and 15DP (1.5% Si), were processed under annealing temperatures of 800–850 °C and over-aging temperatures of 240–300 °C. Higher annealing temperatures increased austenite formation and produced more martensite after cooling, leading to higher strength but reduced ductility at 850 °C due to martensite coarsening. Increasing the over-aging temperature coarsened carbides and reduced strength yet stabilized retained austenite and improved ductility through the TRIP effect. An increase in silicon content suppressed carbide precipitation, promoted carbon enrichment in austenite, refined the ferrite–martensite structure, and significantly enhanced both strength and elongation. Consequently, 15DP steel exhibited superior mechanical properties compared to 05DP steel, exhibiting 90–100 MPa higher tensile strength (+6.2–7.0%), 55–65 MPa higher yield strength (+5.3–6.2%), and 1.4–1.8 percentage points higher total elongation (+10–14%), resulting in a 16–20% increase in the strength–ductility balance (Rm × A). However, due to the relatively high hydrogen embrittlement susceptibility of fresh martensite formed either by the TRIP effect during deformation or after over-aging, 15DP steel did not exhibit substantially improved HE resistance despite its higher retained austenite fraction. Full article