Search Results (1,081)

22Cr12NiMoWV martensitic heat-resistant steel serves as a candidate material for underground coiler sector plates, whereas the coupling relationship between partial austenitization, precipitate/carbide evolution, martensitic interfaces and mechanical response under medium-temperature quenching–tempering conditions is still ambiguous. This work systematically explores four key heat treatment variables to clarify the microstructure–property correlation and strengthening rebalance mechanism. In the 790–830 °C partial austenitization interval, the austenite fraction increases from 36.49 wt.% to 72.32 wt.% with a concurrent decline of M₂₃C₆ carbides from 5.34 wt.% to 4.92 wt.%, demonstrating competitive evolution between austenite generation and carbide retention. Specimens quenched at 810 °C for 2 h deliver a yield strength of 1015.4 ± 13.8 MPa and tensile strength of 1192.9 ± 17.8 MPa, 24.9% and 19.9% higher than conventional QT samples, owing to synergistic reinforcement from α′ martensite matrix, orientation interfaces and Cr-Mo-W-V-rich precipitates. After 400 °C × 4 h tempering, the steel still maintains superior strength, and its average misorientation falls from 40.41° to 31.17°. Though its engineering ductility is inferior to the quenched state, the mixed dimple–quasi-cleavage fracture mode suggests a partial recovery of ductile fracture characteristics compared with over-treated samples. The uncovered strengthening mechanism provides microstructural theoretical support for process optimization. Compared with the conventional quenching and tempering process, the optimized medium-temperature process (810 °C × 2 h quenching + 400 °C × 4 h tempering) reduces energy consumption and the production cycle and provides solid theoretical and experimental data for a green and low-cost industrial heat treatment of coil plates. Full article

Corrosion-resistant coatings with a double-layer structure are deposited on the surface of S30408 stainless steel at welding currents of 170 A, 200 A, and 230 A using metal active gas (MAG) arc welding technology. The influence of welding current on the microstructure, microhardness, wear resistance, and electrochemical corrosion behavior of the coating is systematically studied. The results show that the coating produced at 200 A exhibited the finest martensitic structure, the highest microhardness (~450 HV), and the lowest mass loss (139.9 mg), indicating its superior wear resistance. In contrast, the coating fabricated at 230 A displayed the most positive corrosion potential (−0.302 V vs. saturated calomel electrode (SCE)) in 3.5 wt.% NaCl solution, which is attributed to enhanced elemental homogenization arising from the higher heat input. This paper clarifies the critical role of welding current in balancing wear and corrosion performance and provides a practical guideline for the cost-effective surface enhancement of S30408 steel components. Full article

Mineral-scale deposition remains a persistent flow-assurance and asset-integrity constraint in oil and gas production. Calcium carbonate, calcium sulfate, barium sulfate, iron sulfide, and mixed inorganic scale deposits reduce tubing internal diameter. They also impair near-wellbore permeability, block safety-critical valves, reduce heat-transfer efficiency, and intensify under-deposit corrosion. Conventional management relies on prediction, chemical inhibition, squeeze treatments, acid dissolution, chelation, mechanical scraping, milling, jetting, and operational water management. These methods are indispensable, but each has a restricted operating envelope. Key limitations include mineral selectivity, corrosion risk, environmental discharge, intervention cost, debris generation, and poor effectiveness against chemically resistant sulfate scales, particularly BaSO₄. Ultrasound has therefore attracted interest as a non-chemical technology. Acoustic cavitation, microstreaming, pressure oscillation, mechanical vibration, and micro jetting may suppress nucleation, disturb boundary layers, weaken adhesion, and fragment brittle deposits. This review critically evaluates ultrasound-assisted scale prevention and removal, with emphasis on production tubing and oilfield relevance. Existing studies show credible mechanistic plausibility and promising laboratory performance for CaCO₃, CaSO₄/gypsum, KCl, NaCl, and membrane or heat-transfer fouling systems. It also compares performance metrics, field cases, and technology-readiness barriers. The evidence is less mature for long steel tubulars operating under high-pressure, high-temperature, multiphase production conditions. Current evidence positions ultrasound at technology-readiness level (TRL) 3–4 for CaCO₃ and CaSO₄ systems, where laboratory and bench-scale validation is established, and at TRL 2–3 for BaSO₄, where mechanistic plausibility exists but controlled experimental validation remains absent. The technology is not yet at the pilot–production transition for downhole tubing applications, but it is approaching that threshold for surface process equipment. Its most credible near-term role is as an intensifier paired with low-dose chemical inhibitors, where acoustic boundary-layer disruption can reduce the minimum inhibitory concentration threshold of inhibitors, and with mild chelating agents for early-stage BaSO₄ management, where ultrasound-enhanced mass transfer may accelerate chelant penetration into deposit microstructure. Advancing ultrasound from its current TRL toward field qualification requires targeted BaSO₄ scale validation in steel tubing systems, acoustic field mapping under HPHT multiphase conditions, mass-removal metrics, and a structured pilot programme. Full article

Resistance spot welding (RSW) is the primary joining technology for automotive advanced high-strength steels (AHSSs), where the inherent severe thermal cycles profoundly alter the heat-affected zone (HAZ) microstructure, leading to localized variations in mechanical properties. Characterizing the spatial gradients in microstructure and the resulting mechanical properties remains a major challenge in weld failure analysis due to the small size of the HAZ and its complex thermal history. In this study, the HAZ of two prominent AHSS grades, a first-generation press hardening steel (PHS1500) and a third-generation quenching and partitioning steel (Q&P1180), was physically simulated using a Gleeble^® 3180 thermomechanical simulator to achieve precise control over the localized thermal cycles. The investigation first evaluated the role of thermal cycle duration, governed by the welding time parameter (300 ms vs. 800 ms), on the microstructural evolution of the PHS1500 steel. Increasing the weld time from 300 ms to 800 ms reduced the cooling rate under the nominal 1400 °C condition from approximately 3000 K/s to 2500 K/s; however, no marked change was observed in the overall microstructural and hardness trends within the investigated range. Subsequently, using the 300 ms thermal profile as a reference baseline, a comparative metallurgical study was conducted between PHS1500 and Q&P1180. Under the same 300 ms thermal history, the maximum hardness reduction relative to the corresponding base material was approximately 42% for PHS1500 and 12% for Q&P1180. The hardness minima were located within FE-estimated temperature ranges close to the Ac₁ region for PHS1500 and around 600 °C for Q&P1180, respectively. This comparison highlighted the distinct microstructural responses of the two generations across the upper-critical (UCHAZ), inter-critical (ICHAZ), and sub-critical (SCHAZ) zones. Moreover, microhardness profiles were correlated with the microstructural findings, establishing a correlation among the simulated thermal history, the observed microstructural evolution, and localized mechanical performance. Full article

Ultra-supercritical (USC) steam turbines combine severe steam conditions with increasingly frequent start-up, shutdown, and load-following operations. Their main steam valves must preserve pressure boundary integrity, sealing, and rapid actuation while non-uniform heating, creep, cyclic plasticity, oxidation, wear, and contact redistribution alter component geometry. However, the relevant evidence remains fragmented across alloy development, component thermo-mechanics, valve aerodynamics, and lifetime monitoring. This short, mechanism-oriented review integrates these domains through a material structure–function framework in which deformation relative to assembly clearance governs jamming risk. It synthesizes evidence on heat-resistant body and surface materials, 9–12% Cr steel stability, weldability and repair sensitivity, and cold, warm, and hot start-up histories. It also evaluates creep–fatigue interaction, contact, flow-induced vibration, multi-physics modeling, validation, uncertainty, monitoring, and digital twins. The synthesis shows that neither peak equivalent stress nor steady-state temperature alone can establish functional reliability. Credible assessment requires temperature-dependent material data, realistic steam-side heat transfer, cyclic constitutive behavior, initial and residual clearances, manufacturing and assembly tolerances, state-dependent friction, uncertainty analysis, and corroborating plant or inspection evidence. The most consequential research needs are valve-level validation datasets, thermal contact testing, function-oriented life criteria, and uncertainty-aware digital twins that jointly inform materials, geometry, and transient operation. 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

In this work, the microstructural evolution and comprehensive performances (mechanical, wear, and corrosion resistance) of LDED-fabricated 2205 DSS subjected to heat treatment at 1000 °C for different holding durations (5 min, 10 min, 30 min, and 60 min) were systematically investigated. The results indicate that the austenite content gradually increases with the extension of heat treatment time, reaching a peak value of 51% at 30 min. Meanwhile, the austenite morphology transforms from dendritic grains to equiaxed grains, accompanied by the massive precipitation of intragranular austenite (IGA) and obvious elemental enrichment behavior. In terms of mechanical and functional performances, the microhardness decreases slightly with prolonged heat treatment, with a total reduction of only 7%. The elongation increases continuously, while the yield strength and tensile strength remain relatively stable. Additionally, the wear coefficient and wear rate present a trend of first decreasing and then increasing. The minimum wear rate of 48.32 × 10⁻⁶ mm³/(N·m) is obtained at the heat treatment duration of 30 min, which is 83.4% lower than that of the untreated sample. Moreover, the optimal corrosion resistance is achieved after 30 min of heat treatment, with the corrosion current density decreasing by 45.8% relative to the as-built specimen. These results demonstrate that heat treatment at 1000 °C for 30 min is an optimal processing parameter to significantly optimize the microstructure and comprehensive performances of LDED-2205 DSS. Full article

This paper investigates the design of aluminium I-beams under major axis bending, fabricated by MIG welding three plates to form the section. The study focuses on beam sizes relevant to pedestrian bridges, with depths ranging from 508 mm to over 2540 mm. The analysis is limited to local buckling behaviour. A total of 600 geometrical material non-linear imperfection analysis-GMNIA and linear buckling analysis-LBA reference numerical results were obtained from validated non-linear shell finite element models. The influence of the heat-affected zone (HAZ) is shown to be pronounced and detrimental to the resistance of welded aluminium beams. Unlike in steel beams, where buckling often governs, local buckling modes in aluminium members may arise but are typically dominated by HAZ-related failure. The effect of strain hardening on the behaviour and resistance of aluminium alloys is examined and compared with current design approaches, which typically assume an idealised plastic plateau similar to steel. The results show that strain hardening significantly enhances resistance and is not captured by existing design methods. The effect of residual stresses in welded aluminium members is also investigated. The results indicate that MIG-induced residual stresses are sufficiently small and have a negligible influence on both structural behaviour and strength. Their effect can be conservatively accounted for by increasing the amplitude of initial geometric imperfections. The study shows that current design recommendations are inconsistent and mostly unsafe for welded aluminium beams bridge sections governed by local buckling. The findings provide improved insight into the behaviour and resistance of such members and contribute to more accurate and efficient design methods. Full article

The decarbonization of industrial heating systems is one of the major challenges of the current energy transition. Gas-fired radiant tubes dominate industrial heating in large-span, high-bay buildings due to their high efficiency and low operating costs; however, the absence of equivalent electric solutions capable of replacing them represents a significant technological and scientific gap. This paper presents the design, construction, and experimental characterization of an innovative electric radiant tube prototype developed within the INFRAEL research project. The prototype consists of a 100 mm diameter steel tube housing nickel–chromium resistive elements in various configurations, powered from a 230 V AC supply. Thermal measurements were performed using Type K thermocouples distributed along the tube, a non-contact infrared thermometer, and thermovision imaging, complemented by MATLAB R2025bTrial-based interpolation for mapping the thermal field on a receiving plane placed 2 m below the tube. Experimental results show that at a total power of ~1.2 kW (two resistors in parallel), the tube surface reaches temperatures exceeding 250 °C, corresponding to medium-wave infrared emission (~4 μm). A single 630 W resistor yields surface temperatures of approximately 136–160 °C. The temperature distribution on the receiving plane is relatively uniform. The study identifies key optimization directions—resistor geometry, thermal insulation, and integration with photovoltaic sources—with the goal of developing a competitive, zero-carbon alternative to gas-fired radiant heating systems in industrial environments. Full article

The present study is situated within the broader research context of optimizing the use of C60 steel in industrial applications, with a particular emphasis on enhancing durability and fatigue resistance, two critical factors in the field. C60 steel is renowned for its exceptional combination of strength and hardness. However, a critical evaluation is necessary to ascertain the impact of thermal and thermochemical treatments on its performance under fatigue conditions. An investigation was conducted into the crack formation process and the early stages of fatigue in C60 steel. The effects of heat treatment (hardening and tempering) were compared with those of thermochemical treatments (oxidation) on the steel’s microstructure. Furthermore, the performance of C60 steel under fatigue conditions was evaluated based on the applied treatments. The insights gained from this research can optimize the use of this steel in industries requiring high resistance and durability. The study’s methodology encompassed the execution of fatigue tests on a four-point bending machine, a procedure that was meticulously employed to ascertain the onset of microcracking. The C60 steel samples were processed in accordance with SR ISO 1099:2017, entitled “Fatigue testing. Axial load method”. To ensure consistency and comparability of results, the samples were fabricated from the same material charge and machined under identical conditions. A total of 26 samples were utilized, with 13 samples allocated to each treatment type: heat treatment by hardening, tempering, and thermochemical treatment by oxidation. To ensure comparability and scientific interpretability of the results, an identical applied force level was utilized for both treatment conditions. The frequency changes were monitored to evaluate the behavior of the materials under repeated stresses. Finally, the frequency changes were correlated with the number of cycles to identify when microcracks appeared and their evolution. The primary findings of this study indicate substantial disparities between the longevity of thermally and thermochemically modified specimens and the onset of microcrack formation in the material. Full article

Metal centralizers suffer high frictional resistance, high self-weight, and severe pore shrinkage after perforation in deep, highly deviated, and horizontal wells. Targeting the performance demands of adhesive casing centralizers, this study uses epoxy resin as the matrix, introduces amino modification, and regulates inorganic filler composites to prepare an amino-modified epoxy resin composite centralizer material, followed by systematic property tests. The optimal formula of modified epoxy resin:curing agent:UR300 accelerator:amino-modified silica:silicon carbide:alumina is 100:10:1:1:35:20 and delivers superior comprehensive performance. Its compressive strength reaches 136.61 MPa with a Shore hardness of 92.32 HD, low linear expansion, and favorable thermal compatibility with steel casings. Hardness remains stable after 168 h of aging at 150 °C, and the material maintains low friction at ambient and elevated temperatures. After 30-day immersion in acidic, alkaline, and high-salinity fluids, its compressive strength retention exceeds 86% with a slight variation in volume and mass, while adhesion strength reaches 2.667 MPa at a pipe-wall roughness of 12.12 μm. Combining high strength, heat resistance, corrosion resistance, and strong adhesion, the material suits complex downhole conditions and supports the field application of resin composite centralizers. Full article

Relatively low-cost titanium carbide (TiC) materials and metal matrix composites (MMC) are proposed for waste-to-hydrogen conversion. Two types of steels are used as bases prepared from EN 10088 flat products, namely X2CrTi12 (1.4512, AISI 409) and X5CrNi18-10 (1.4301, AISI 304). TiC is mixed with TRIBALOY^® T-800 alloy in powder form and applied via laser-directed energy deposition (DED-LB) over the substrates. For the powder mixture, Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) are performed. The raw materials are investigated for the processes that occur in them under heating. After the solidification of the molten mixture, grinding and polishing are performed to achieve a thin layer. The studies of the obtained MMC include interface zone assessment, hardness and Young’s modulus distribution, microstructural analysis, and visual defect evaluation. Advanced sensors for acoustic emission (AE) and Electrical Contact Resistance (ECR) provided characterization together with micro-scratch testing. The use of photoluminescence spectroscopy is proposed for the new composite materials. The electron transfer pathway can be studied with time-resolved spectroscopy. Renewable energy production by breaking down waste into hydrogen-rich syngas can be achieved through pyrolysis, followed by steam reforming and purification. The obtained novel materials show promising application solutions with increased durability, corrosion, and wear resistance. Full article

With contemporary advancements in additive manufacturing (AM), it has become possible to obtain hull structures for spacecraft made of relatively cheap materials. The possibility of substituting super-austenitic stainless steel Avesta SMO 254 X1NiCrMoCuN20-18-7 (EN 10088) for that already used in the Starship SpaceX 304 L-Modified is focused on achieving better thermal stability and durability in extreme conditions. The Directed Energy Deposition Arc (DED-Arc) method for AM has enabled the production of high-strength-to-weight ratios. The aim is to engage low-cost material with treatment optimization to provide greater corrosion resistance and high yield and tensile strength. For the DED-Arc, a filler wire was selected for the welding source, Fronius TPS 400i. A simulation via the RoboDK Robot Development Kit for the FANUC ARC Mate 100ID10L is provided. Additional shot pining/vibration treatment is proposed for the finished structure, which can be a substitute for the cold-worked initial metal. A comparison is made for stainless steel that has already been tested for space travel. Regimes for the manufacturing process are proposed, with representative samples of Avesta SMO 254 obtained and tested using microhardness measurements, microcracking detection, porosity measurements, interface zone assessment, and microstructural analysis. The DED-Arc process can be applied to large-space shell manufacturing. A comparison is made with a focus on the mechanical and corrosion advantages. For Avesta SMO 254, microhardness measurements ranged from 235 to 246 HV1 and increased after treatment. The controlled parameters provided a maximum heat input of 0.7 KJ/mm, no defects, and a fine microstructure. The successful use of stainless steel with AM increases the potential for multiple space missions. The advanced method shows high quality, allows cost savings and provides extended service life. Full article

The influence of different heat treatment processes on the microstructure and mechanical properties of 18Ni350 maraging steel manufactured by selective laser melting and the corrosion resistance of TiB₂ ceramic coatings Electro-Spark-Deposited on its surface when immersed in high-temperature molten aluminum have been investigated in the present study. The microstructures and mechanical properties of the differently heat-treated samples were analyzed using various precision instruments. The results reveal that the as-built sample exhibits a microstructure composed of cellular and columnar dendritic grains. After solution treatment, the microstructure fully transforms into lath-like martensite. After direct aging treatment, the cellular structures diminish, while precipitates at grain boundaries proliferate with increasing aging temperature. SAT- treatment achieves full microstructural homogenization, featuring fine-lath martensite and a small amount of randomly distributed austenite particles. DA- and SAT- significantly improve the strength, hardness and modulus of samples and were found to reduce the toughness and plasticity. After solution treatment at 800 °C for 1 h followed by aging treatment at 520 °C for 6 h (SAT 800-520), the specimen achieved an UTS of 2476 MPa while maintaining an EL of 4.6%. The TiB₂ coating and the Cr interlayer deposited via ESD form a continuous interfacial bond with the substrate, demonstrating favorable adhesion. After 4 h of static immersion in high-temperature molten aluminum, the coating remains intact without complete delamination, delivering effective protection to the substrate. Full article

Quenched and tempered (Q+T) bolt steels are widely used in key load-bearing structures such as bridges, wind power equipment, pressure vessels and engineering machinery, but they are susceptible to hydrogen-induced cracking under applied stress during service. In this study, a bolt steel was subjected to Q+T heat treatment, including quenching at 850, 900, 950, 1000 and 1050 °C, followed by tempering at 500 °C. Microstructural characterization, hydrogen permeation tests, and slow strain rate tensile tests were conducted to investigate the effects of quenching temperature on microstructural evolution, hydrogen diffusion behavior and resistance to hydrogen-assisted cracking. As the quenching temperature increased from 850 °C to 1050 °C, the prior austenite grains, packets and blocks were gradually coarsened, the fraction of high-angle grain boundaries decreased from 64.7% to 54.2%, and although partial dissolution of primary carbides may occur during austenitizing, the number/area fraction and size of carbides observed in the final tempered martensitic microstructure increased after the subsequent tempering treatment. Meanwhile, the Nb/Ti-rich precipitates changed only slightly, and the dislocation density increased. The effective hydrogen diffusion coefficient, D_eff, increased with increasing quenching temperature, mainly because grain coarsening significantly reduced the high-angle grain boundary area and weakened the hydrogen-trapping effect of grain boundaries. This dominant effect masked the diffusion-retarding effects caused by increased dislocation density and coarser carbides. With increasing quenching temperature, the strength loss ratio increased from 7.3% to 12.0%, and the plasticity loss ratio increased from 10.0% to 13.6%, indicating enhanced hydrogen-assisted cracking susceptibility. The fracture morphology gradually changed from deep dimples to flat dimples and flattened ductile–brittle mixed features, while the crack propagation path became straighter. A higher quenching temperature weakened the blocking effect of grain boundaries on crack propagation and reduced the resistance of the quenched and tempered bolt steel to hydrogen-assisted cracking. Full article