Search Results (77)

Duplex stainless steel is widely used in nuclear power, the chemical industry, coastal infrastructure, and other fields due to its excellent mechanical properties, physical properties, and corrosion resistance. This paper focuses on the narrow-gap groove laser welding with wire filling conducted on 25 mm S32101 duplex stainless steel. It analyzes the microstructural features of various regions within the welded joint and evaluates its mechanical properties and corrosion resistance. Research indicates that the thermal cycle effect during multi-layer and multi-pass welding significantly affects the microstructure and properties of the joint. Austenite in the weld seam area mainly precipitates along the dendrite boundaries; in the overlap area of the weld beads, due to the secondary thermal cycle effect, the austenite content significantly increases to 56.2%, and the grain size is refined; in the heat-affected zone (HAZ) near the seam, austenite appears in stripes, and its content decreases to 39.4%. Mechanical property tests reveal that the welded joint exhibits an average tensile strength of 705 MPa, surpassing that of the base material. The corrosion resistance of the weld zone closely mirrors that of the base material, yet the corrosion resistance of the heat-affected zone (HAZ) is diminished due to the reduction in austenite content and the potential precipitation of harmful phases. Full article

The bioinspired superhydrophobic surfaces have demonstrated many fascinating performances in fields such as self-cleaning, anti-corrosion, anti-icing, energy-harvesting devices, and antibacterial coatings. However, developing a low-cost, feasible, and scalable production approach to fabricate robust superhydrophobic surfaces has remained one of the main challenges in the past decades. In this paper, we propose an uncommon method for the fabrication of a durable superhydrophobic coating on the surface of the glass slide (GS). By utilizing the screen printing method and high-temperature curing, the epoxy resin grid (ERG) coating was uniformly and densely loaded on the surface of GS (ERG@GS). Subsequently, the hydrophobic silica (H-SiO₂) was deposited on the surface of ERG@GS by the impregnation method, thereby obtaining a superhydrophobic surface (H-SiO₂@ERG@GS). It is demonstrated that the micro-grooves in ERG can provide a large specific surface area for the deposition of low surface energy materials, while the micro-columns can offer excellent protection for the superhydrophobic coating when it is subjected to mechanical wear. It is important to note that micro-columns, micro-grooves, and nano H-SiO₂ jointly form the micro–nano structure, providing a uniform and robust rough structure for the superhydrophobic surface. Therefore, the combination of a micro–nano rough structure, low surface energy material, and air cushion effect endow the material with excellent durability and superhydrophobic property. The results show that H-SiO₂@ERG@GS possesses excellent self-cleaning property, mechanical durability, and chemical stability, indicating that this preparation method of the robust superhydrophobic coating has significant practical application value. Full article

Gas well deliquification is a key technology for mitigating liquid loading and restoring or enhancing production capacity in ultra-deep, high-temperature, and high-pressure gas wells. The abnormal corrosion behavior observed in the gas lift tubing of the Well X-1 oilfield in western China, within the 50–70 °C interval (1000–1500 m), was investigated. By analyzing the asymmetric wall thinning and axial groove morphology on the inner surface of tubing and then establishing a two-dimensional model of the vertical wellbore, the gas–liquid flow behavior and associated corrosion mechanisms were also elucidated. Results indicate that the flow pattern evolves from slug flow at the bottomhole, through a transitional pattern below the gas lift valve, to annular-mist flow at and above the valve. The wall shear stress peaks at the gas lift valve coupled with the significantly higher fluid velocity above the valve, which markedly elevates the corrosion rate. In this regime, the resultant annular-mist flow features a high-velocity gas core carrying entrained droplets, whose impingement synergistically enhances electrochemical corrosion, forming severe groove-like morphology along the inner tubing wall. Therefore, the corrosion in this well is attributed to the synergistic effect of the mechano-electrochemical coupling between multiphase flow and electrochemical processes on the inner surface of the tubing. Full article

Environmental factors significantly affect the fatigue performance of weathering steel welded components in high-altitude, low-temperature corrosive environments. This study conducted multi-factor-coupled constant-amplitude fatigue tests on Q500qENH weathering steel V-groove welded joints and built an equivalent finite element model using test data to explore key influencing factors under multi-condition coupling. Results show that stress level most significantly affects fatigue performance, followed by corrosion duration, then ambient temperature, with influences decreasing in turn. Analyzing 18-day cyclic immersion corrosion morphology predicts 21-year outdoor corrosion in plateau regions, providing a reliable method for long-term exposure prediction. Finite element simulations confirm that low temperatures improve slightly corroded specimens’ fatigue performance by 20%, but damage accumulates before optimal service. This study offers key parameters for safe design of high-altitude weathering steel welded components. Full article

AISI 304 stainless steel is widely used in the equipment manufacturing industry due to its excellent corrosion resistance. However, its high toughness and plasticity lead to severe tool wear during machining, significantly shortening the tool’s life. To mitigate tool wear, this study designed and fabricated a novel micro-groove structure on the tool’s rake face, aiming to reduce friction and thermal stress. The performance of the micro-groove tool was evaluated through cutting simulations and durability tests. Results demonstrate that this micro-groove structure effectively reduces cutting forces, suppresses tool wear, and improves chip control and heat dissipation. Full article

Ti-Mo-N coatings were deposited on GCr15 bearing steel using arc ion plating. The effect of deposition bias on the coating microstructure, mechanical properties, tribological behavior, and electrochemical corrosion resistance was systematically investigated. The coating prepared at −120 V bias showed optimal overall performance. It achieved the lowest friction coefficient (0.308) and lowest wear rate (1.99 × 10⁻⁶ mm³/N·m). The significant improvement in tribological performance is attributed to the lubricating phase formed during the friction process. XPS analysis confirmed the layered MoO₃ formation within the wear scar. Deposition bias also significantly influenced the coating texture. At −120 V, the coating exhibited the strongest (111) crystal plane preferred orientation. This texture strongly correlated with performance enhancement. Regarding electrochemical corrosion, the −120 V coating displayed the lowest corrosion current density (3.62 × 10⁻⁹ A/cm²) and best corrosion resistance. Its corrosion morphology showed no obvious pitting, grooves, or other damage features. The results demonstrate the critical role of deposition bias in tailoring Ti-Mo-N coating properties. This research provides essential experimental support and a theoretical basis for designing wear- and corrosion-resistant protective coatings on bearing steel. Full article

One of the most critical aspects of turning, and machining in general, is the surface roughness of the finished product, which directly influences the performance, functionality, and longevity of machined components. The accurate prediction of surface roughness is vital for enhancing component quality and machining efficiency. This study presents a machine learning-driven framework for modeling mean roughness depth (Rz) during the dry machining of super duplex stainless steel (SDSS 2507). SDSS 2507 is known for its exceptional mechanical strength and corrosion resistance, but it poses significant challenges in machinability. To address this, this study employs flank-face textured cutting tools to enhance machining performance. Experiments were designed using the L₂₇ orthogonal array with three continuous factors, cutting speed, feed rate, and depth of cut, and one categorical factor, tool texture type (dimple, groove, and wave), along with surface roughness as an output parameter. Gaussian Data Augmentation (GDA) was employed to enrich data variability and strengthen model generalization, resulting in the improved predictive performance of the machine learning models. MATLAB R2021a was employed for preprocessing, the normalization of datasets, and model development. Two models, Least-Squares Support Vector Machine (LSSVM) and Multi-Gene Genetic Programming (MGGP), were trained and evaluated on various statistical metrics. The results showed that both LSSVM and MGGP models learned well from the training data and accurately predicted Rz on the testing data, demonstrating their reliability and strong performance. Of the two models, LSSVM demonstrated superior performance, achieving a training accuracy of 98.14%, a coefficient of determination (R²) of 0.9959, and a root mean squared error (RMSE) of 0.1528. It also maintained strong generalization on the testing data, with 94.36% accuracy and 0.9391 R² and 0.6730 RMSE values. The high predictive accuracy of the LSSVM model highlights its potential for identifying optimal machining parameters and integrating into intelligent process control systems to enhance surface quality and efficiency in the complex machining of materials like SDSS. Full article

Fans are essential electronic components for heat dissipation in electronic systems, with fan bearings being critical parts that determine fan performance and lifespan. This paper investigates the corrosion, wear, power consumption, temperature, and vibration characteristics of a newly designed and manufactured powder metallurgy bearing with herringbone oil grooves for fans under high-humidity and high-temperature conditions. Corrosion experiments on iron–copper powder metallurgy bearings show that a higher environmental temperature and humidity result in greater corrosion current and reduced corrosion resistance. Bearings operated under high humidity (85% RH) and a high temperature (80 °C) for 0, 3, and 8 days, respectively, revealed that wear and corrosion occur simultaneously. The longer the operating time, the more significant the wear and corrosion. After 3 and 8 days, the lubricating oil flow in the oil grooves decreased by 9.8% and 51.5%, respectively. When bearings subjected to varying degrees of corrosion were tested under the same standard operating conditions, it was found that the bearings corroded for 3 and 8 days, resulting in a significant increase in the number of wear debris particles, higher RMS vibration values, and a power consumption increase of 6.9% and 7.8%, respectively. The percentage of iron elements on the surface gradually decreased, with the copper elements being the primary wear particles during the wear process. However, due to the increased clearance between the rotating shaft and the bearing caused by wear, the fan temperature slightly decreased with increased surface wear. Full article

To explore the feasibility of preparing Zn alloy bulk, Zn-6Cu deposit was prepared by cold-spraying additive manufacturing. Microstructure, tensile and wear behavior were investigated before and after heat treatment. Cold-sprayed Zn-6Cu deposit was constituted by irregular flattening particles and pores after heat treatment. Zn-6Cu deposits were composed of Zn and CuZn₅ phases in addition to ZnO phase regardless of heat treatment, but the full width at half maximum of both the CuZn₅ and the Zn phase were varied. The yield strength and ultimate tensile strength of Zn-6Cu deposits after post heat treatment were, respectively, increased from 83.8 ± 28.7 MPa and 159.6 ± 44.5 MPa to 89.4 ± 24.4 MPa and 223.8 ± 37.1 MPa. Fracture morphology after tensile testing exhibited main features of dimples, pores and cleaving particles. The friction coefficient and wear rate of Zn-6Cu deposits were increased after heat treatment, and the corrosive wear exhibited a lower friction coefficient and wear rate than the dry wear due to the lubricant of simulated body fluid. Grooves and localized delamination were the main wear features of Zn-6Cu deposits regardless of both the heat treatment and wear condition. This result indicates a potential application of cold-sprayed Zn-6Cu deposits comparable to the casting ones. Full article

The high-speed plough tip is the core soil-touching component in southern Xinjiang field cultivation, but the interaction of the plough tip with the soil results in severe wear of the tip. The friction behaviour of sand and soil on plough tips was investigated with a homemade rotary abrasive wear tester in a one-factor multilevel test with three parameters: moisture content, velocity/rotational speed and friction distance. The objective was to study the friction behaviour of the sand soil and plough tip and analyse and characterise the wear amount, wear thickness and compressive stress distribution, three-dimensional wear morphology and microscopic wear morphology of the plough tips. The results show that with increasing speed, the wear amount changes more gently; with increasing soil water content, the soil adhesion force and lubricating water film increase so that the wear amount follows a second-order parabolic law; and with increasing friction distance, the wear amount gradually increases, and the wear rate also shows an upward trend when the plough tip is in the abrasive wear stage. The tip makes contact with the firmer soil with higher surface compressive stresses, causing the most wear. As the friction distance increases, sand particles become embedded in the contact surfaces, creating a groove effect along with spalling pits caused by fatigue wear. During the whole wear period, the groove effect is always accompanied by spalling pits appearing repeatedly. The analysis of the wear micromorphology of the plough tip shows that the number of flaking pits gradually decreases in the direction of soil movement, and the form of damage changes from impact wear to plough groove scratches. Abrasive wear interacts with corrosive wear to exacerbate plough tip wear. Full article

Difficult-to-cut titanium matrix composites (TiB+TiC)/Ti6Al4V have extensive application prospects in the fields of biomedical and aerospace metal microcomponents due to their excellent mechanical properties. Jet electrochemical micromilling (JEMM) technology is an ideal method for machining microstructures that leverages the principle of electrochemical anodic dissolution. However, the matrix Ti6Al4V is susceptible to passivation during electrochemical milling, and the inclusion of high-strength TiB whiskers and TiC particles as reinforcing phases further increases the machining difficulty of (TiB+TiC)/Ti6Al4V. In this study, a novel approach using NaCl+NaNO₃ mixed electrolyte for the JEMM of (TiB+TiC)/Ti6Al4V was adopted. Electrochemical behaviors were measured in NaCl and NaCl+NaNO₃ electrolytes. In the mixed electrolyte, a higher transpassive potential was required to break down the passive film, which led to better corrosion resistance of (TiB+TiC)/Ti6Al4V, and the exposed reinforcing phases on the dissolved surface were significantly reduced. The results of the JEMM machining indicate that, compared to NaCl electrolyte, using mixed electrolyte effectively mitigates stray corrosion at the edges of micro-grooves and markedly improves the uniformity of both groove depth and width dimensions. Additionally, the surface quality was noticeably improved, with a reduction in Ra from 2.84 μm to 1.03 μm and in Rq from 3.41 μm to 1.40 μm. Full article

Molybdenum is an important material in modern industry, widely used in extreme environments such as rocket engine nozzles and microelectrodes due to its high melting point, excellent mechanical properties, and thermal conductivity. However, as a difficult-to-machine metal, traditional machining methods struggle to achieve the desired microstructures in molybdenum. Electrochemical machining (ECM) offers unique advantages in manufacturing fine structures from hard-to-machine metals. Studies have shown that molybdenum exhibits a fast corrosion rate in alkaline or acidic solutions, posing significant environmental pressure. Therefore, this study investigates the electrochemical machining of molybdenum in neutral salt solutions to achieve high-precision microstructure fabrication. First, the polarization curves and electrochemical impedance spectroscopy (EIS) of molybdenum in NaNO3 solutions of varying concentrations were measured to determine its electrochemical reaction characteristics. The results demonstrate that molybdenum exhibits good electrochemical reactivity in NaNO3 solutions, leading to favorable surface erosion morphology. Subsequently, a mask electrochemical machining technique was employed to fabricate arrayed microstructures on the molybdenum surface. To minimize interference between factors, an orthogonal experiment was used to optimize the parameter combination, determining the optimal machining process parameters. Under these optimal conditions, an array of micro-groove structures was successfully fabricated with an average groove width of 110 μm, a depth-to-width ratio of 0.21, an aspect ratio of 9000, and a groove width error of less than 5 μm. Full article

Drilling risers play a crucial role in deepwater oil and gas development, and any compromise in their integrity can severely hinder the progress of drilling operations. In light of this, efficient and accurate nondestructive testing of drilling risers is paramount. However, existing inspection equipment falls short in both efficiency and accuracy, posing challenges to the sustainability of deepwater oil and gas exploration and development. To effectively assess the damage conditions of deepwater drilling risers, this study developed an inspection robot based on metal magnetic memory and researched intelligent defect recognition methods using computer vision. The robot can perform in situ inspections on drilling risers and has been successfully deployed for field application on a deepwater drilling platform. The application results demonstrate that this detection robot offers significant advantages regarding high reliability and detection efficiency. Utilizing data collected on-site, we constructed a dataset containing 1100 images that cover five typical types of defects in drilling risers, including pitting, groove corrosion, and wear. Based on this dataset, we proposed and trained a novel image classification model, SK-ConvNeXt-KAN. By deeply optimizing the ConvNeXt convolutional network incorporating the introduced SK attention module and replacing traditional linear classification layers with the KAN module, this model significantly enhanced its feature extraction capabilities and efficiency in handling complex nonlinear problems. Experimental results show that this model achieved an accuracy rate of 95.4% in identifying defects in drilling risers, which is significantly better than traditional methods. This achievement has dramatically improved the efficiency and accuracy of deepwater drilling riser inspections, providing robust technical support for deepwater oil and gas exploration and development sustainability. Full article

Bearing steel (GCr15) is widely used in key parts of mechanical transmission for its excellent mechanical properties. Electrochemical machining (ECM) is a potential method for machining GCr15, as the machining process is the electrochemical dissolution of GCr15 regardless of its high hardness (>50 HRC). In ECM, NaNO₃ solution is a popular electrolyte, as it has the ability to help in the nonlinear dissolution of many metallic alloy materials, making it useful for precision machining. However, due to high carbon content of GCr15, the electrochemical dissolution of GCr15 is unique, and there is always a black layer with high roughness on the machined surface, reducing the surface quality. In order to improve the electrochemical machining of GCr15 with a high surface quality, the surface characteristics of GCr15 in ECM were investigated. The anodic polarisation curve in the NaNO₃ electrolyte was measured and electrochemical dissolution experiments were conducted with different current densities. SEM, XRD, and XPS were employed to analyse the surface morphology and composition formed on the machined surface at different current densities. The initial results showed that there were two parts (black part and bright part) formed on the machined surface when a short circuit occurred, and the test results suggested that the black part contained a mass of Fe₃O₄ while the bright part was composed of mainly Fe and Fe₃C. Further investigation uncovered that a black flocculent layer (Fe₃O₄) always formed in a low current density (32 A/cm²) with high roughness. With the current density increased, the amount of black flocculent layer was reduced, and Fe₃C particles appeared on the machined surface. When the current density reached 81 A/cm², the entire flocculent oxide layer was removed, only some spherical Fe₃C particles were inserted on the machined surface, and the roughness was reduced from Ra7.743 μm to Ra1.783 μm. In addition, due to exposed Fe₃C particles on the machined surface, the corrosion resistance of the machined surface was significantly improved. Finally, circular arc grooves of high quality were well manufactured with current density of 81 A/cm² in NaNO₃ electrolyte. Full article

Preparing elastic substrates as a carrier for dual-end supported nickel chromium thin film strain sensors is crucial. Wet etching is a vital microfabrication process widely used in producing microelectronic components for various applications. This article combines lithography and wet etching methods to microprocess the external dimensions and rectangular grooves of 304 stainless steel substrates. The single-factor variable method was used to explore the influence mechanism of FeCl₃, HCl, HNO₃, and temperature on the etching rate, etching factor, and etching surface roughness. The optimal etching parameter combination was summarized: an FeCl₃ concentration of 350 g/L, HCl concentration of 150 mL/L, HNO₃ concentration of 100 mL/L, and temperature of 40 °C. In addition, by comparing the surface morphology, microstructure, and chemical and mechanical properties of a 304 stainless steel substrate before and after etching treatment, it can be seen that the height difference of the substrate surface before and after etching is between 160 μm and −70 μm, which is basically consistent with the initial design of 0.2 mm. The results of an XPS analysis and Raman spectroscopy analysis both indicate that the surface C content increases after etching, and the corrosion resistance of the surface after etching decreases. The nano-hardness after etching increased by 26.4% compared to before, and the ζ value decreased by 7%. The combined XPS and Raman results indicate that the changes in surface mechanical properties of 304 stainless steel substrates after etching are mainly caused by the formation of micro-nanostructures, grain boundary density, and dislocations after wet etching. Compared with the initial rectangular substrate, the strain of the I-shaped substrate after wet etching increased by 3.5–4 times. The results of this study provide the preliminary process parameters for the wet etching of a 304 stainless steel substrate of a strain measuring force sensor and have certain guiding significance for the realization of simple steps and low cost of 304 stainless steel substrate micro-nano-processing. Full article