Search Results (781)

Wire Arc Additive Manufacturing (WAAM) is a cost-effective and scalable technique for producing large metallic components; however, coarse columnar microstructures, strong crystallographic texture, and significant residual stresses limit its widespread adoption. Hybrid WAAM processes that integrate deformation-based techniques have been developed to address these limitations. This review provides an analysis of deformation-assisted WAAM, covering interlayer rolling, friction stir processing (FSP), machine hammer peening, laser shock peening, and ultrasonic-vibration-assisted techniques. These hybrid techniques introduce additional thermomechanical parameters (strain, strain rate, and applied stress) that significantly influence microstructure evolution. The governing physical metallurgy mechanisms are discussed in detail, including dislocation accumulation, recovery, static and dynamic recrystallization, and severe plastic deformation. Studies from 2022 to 2025 are critically reviewed, highlighting the effectiveness of hybrid WAAM in promoting columnar-to-equiaxed grain transformation, reducing anisotropy, mitigating defects, and improving mechanical properties across aluminum, titanium, steels, and nickel-based alloys. The integration of auxiliary processes such as in situ machining and heat treatment is also discussed. This review establishes a process–structure–property framework for hybrid WAAM and provides guidance for the development of advanced additive manufacturing systems for the production of near-net-shape components, with reported yield-strength gains of 20–40%, elongation gains of 10–30%, and fatigue-life improvements of up to 60% relative to as-built WAAM. Full article

Studies were conducted on the effect of the partial substitution of nickel in an LaNi₅ alloy with germanium (5% by weight) or magnesium (3.3% by weight), in addition to surface modification using phosphomolybdic heteropolyacid (MPA) on the course of corrosion and passivation processes of hydrogen electrodes in a highly alkaline environment. The investigations were carried out by means of electrochemical impedance spectroscopy (EIS) and the potentiodynamic methods to analyse changes in the electrochemical parameters as a function of exposure time. The surface topography of the electrodes and chemical composition were investigated utilising a KEYENCE VHX-7000 digital microscope (Osaka, Japan) and a scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy EDS X-ray microanalysis attachment. The novelty of this work lies in the systematic, time-dependent comparison of the effects of bulk and surface modifications on the evolution of corrosion-passivation mechanisms of electrodes based on the LaNi₅ alloy. It has been shown that the Mg and Ge additives improve corrosion resistance in the initial stage of exposure but lead to destabilisation of the passive layer during prolonged electrolyte interaction. A different effect was observed for the MPA-modified electrodes, in which a stable protective layer forms, limiting corrosion while maintaining favourable hydrogen desorption kinetics. The obtained results indicate the key role of exposure time (>140 h) in shaping the corrosion mechanisms and emphasise the need for simultaneous optimisation of the alloy composition and surface properties in the design of durable hydrogen electrodes. Full article

This study introduces a novel type of oscillating laser directed energy deposition (OL-DED) technology aimed at improving microstructure uniformity and enhancing wear resistance. The microstructure and wear resistance of the OL-DED coating were analyzed and compared with those of the traditional non-oscillating laser directed energy deposition (TL-DED) coating. The results indicate that the OL-DED coating exhibits superior performance, and the grain size of the OL-DED coating is significantly smaller than that of the TL-DED coating. Furthermore, the wear resistance of the OL-DED coating at room temperature and high temperatures exceeds that of the traditional TL-DED coating. The wear mechanisms at room temperature are primarily characterized by abrasive wear, adhesive wear, and oxidative wear, whereas those at high temperatures are mainly dominated by abrasive wear and oxidative wear, with a slight contribution from adhesive wear. Full article

Metal carbides (MCs) serve as essential strengthening phases in nickel-based superalloys, so the decomposition of MCs during high-temperature creep is regarded as detrimental to the mechanical properties and service life of these alloys. However, detailed investigations of the MC decomposition process at the microscale remain limited. In this study, the microstructure of MCs (where M is a mixture of Ti and Ta) in a nickel-based superalloy was characterized using aberration-corrected scanning transmission electron microscopy. The MCs exhibit a spherical core–shell structure, with Ta enrichment in the shell and Ti segregation in the core. Moreover, a high density of Cr-rich stacking faults, accompanied by Cr-rich M₂₃C₆ precipitates at their terminations, was identified in the Ti-rich cores, suggesting that these defects may be closely associated with the decomposition of MCs. This study may further expand the fundamental understanding of the interactions between defects and carbide properties. Full article

This review summarizes the base materials, joining methods, filler materials, and principal technical challenges in endoscope joining fabrication, and proposes practical strategies to improve joint reliability under clinical constraints. We conducted a comprehensive search in multiple databases, including Web of Science, Google Scholar, patent databases, Scopus databases, and Medline (via PubMed), for articles on the joining for precision endoscope fabrication, covering the period from 1950 to 2026. We employed the combinations of keywords, “endoscopy”, “minimally invasive surgery”, “welding”, “joining”, “sealing”, “soldering”, “bonding”, and “brazing”. Approximately 500 references were retrieved. After excluding duplicates and irrelevant studies, 158 publications met the inclusion criteria. Data on base materials, joining, processes, filler materials, and technical issues related to sterilization, corrosion, and microstructural evolution were extracted and analyzed. Endoscopes are multi-material systems, involving metallic biomaterials (stainless steels (SSs), titanium alloys, nickel-based alloys, etc.), optical functional materials (glass, sapphire, quartz, etc.), engineering plastics, ceramics, composite materials, and coatings. Joining, sealing, and functional integration have been achieved via adhesive bonding, laser soldering, laser brazing, wave soldering, reflow soldering, fusion welding, and other joining techniques. The main challenges include how to reliably join highly mismatched dissimilar materials, how to fabricate low-residual-stress joints, and how to increase the long-term resistance to sterilization-induced degradation and thermal aging over repeated 100–200 °C thermal cycles. Conventional joining techniques struggle to balance mechanical integrity, joint hermeticity, and long-term stability under such harsh cyclic conditions. The resulting joints may suffer surface yellowing, interfacial debonding, microcracking, delamination, or progressive property degradation during service. We propose the following three strategies to achieve reliable, low-residual-stress, and sterilization-resistant joining of dissimilar materials for endoscopes: (1) A synergistic design that combines thin-film engineering (including evaporation, sputtering, and electroplating) with silver anti-oxidation layers is proposed to reduce residual stresses and to enhance the joint hermeticity. (2) To develop principles for the selection of multi-joining processes to achieve the multi-material integration and functional assembly of dissimilar material components. (3) To develop the laser-based joining methods (fusion, brazing, or braze-welding) for precision control of heat input, bonding quality, and the least damage to the heat-sensitive components. Full article

The Lower Permian M Formation marine carbonate gas reservoir in Block X of the Sichuan Chongqing exploration area has extreme working conditions with moderate H₂S content (0.57%–0.97%), moderate CO₂ content (2.59%–5.59%), and high formation pressure (70–80 MPa). Gas wells face challenges such as multi medium synergistic corrosion, large productivity differences, and limited economic viability. This article addresses the above issues for the first time by analyzing the dual corrosion mechanism, selecting corrosion-resistant pipes (nickel-based alloys/nickel–tungsten alloy coatings), evaluating the adaptability of corrosion inhibitor processes, and real-time monitoring and warning of corrosion risks. A collaborative anti-corrosion technology system of “mechanism material process monitoring” is constructed, and the first successful field implementation was carried out in this block. The experiment shows that the uniform corrosion rate of nickel–tungsten alloy coating under extreme working conditions (122 °C/85 MPa) is only 0.004 mm/a, which is more economical than traditional nickel-based alloys (cost reduction of 69%); CT2 series corrosion inhibitors can selectively inhibit the corrosion rate of gas wells with different water contents (efficiency > 82%). The combination of electromagnetic flaw detection and multi arm wellbore logging technology has achieved dynamic monitoring of downhole pipe corrosion. This system has been successfully applied in seven gas wells in Block X, achieving controllable corrosion risks, cost reduction and efficiency improvement, and providing a replicable technical paradigm for the safe and economic development of marine high-sulfur gas reservoirs. Full article

Ductility dip cracking (DDC) remains a persistent challenge in multipass welds of high-chromium nickel-based alloys used in the nuclear power generation industry. While dynamic recrystallization (DRX) has been observed to arrest DDC crack growth and has been associated with weld regions that experience less DDC, there exists no quantitative relationship between the extent of recrystallization in a microstructure and DDC susceptibility. This research examines the influence of intragranular carbides on DRX behavior and establishes an experimental relationship between DDC susceptibility and extent of recrystallization in high-chromium nickel-based weld metals, novel contributions for this alloy system. In this work, the DRX behavior of the weld metal of high-chromium nickel-based filler metals (FM-52, FM-52M, FM-52i, and FM-52xl) was investigated under controlled thermo-mechanical conditions, and its effect on DDC susceptibility was established. Weld metal specimens were subjected to uniaxial deformation at 1100 °C to a true strain of 2% at strain rates of 10⁻³/s and 10⁻⁴/s using a Gleeble 3800^TM. Recrystallization was quantified using electron backscatter diffraction (EBSD) via grain orientation spread (GOS) analysis and dislocation–precipitate interactions were examined using transmission electron microscopy (TEM). Strain-to-fracture (STF) testing at 950 °C was employed to assess DDC susceptibility as a function of the extent of recrystallization and grain surface area. All tested weld metals exhibited increased recrystallization and grain refinement, as the strain rate decreased from 10⁻³/s to 10⁻⁴ s. The FM-52i weld metal specimens exhibited the highest grain refinement under high temperature deformation, followed by the FM-52xl, FM-52, and FM-52M weld metals with a percent reduction in average grain surface area of 51.22%, 41.66%, 35.48%, and 24.40%, respectively. The FM-52i weld metal specimens also exhibited the highest recrystallization response, followed by FM-52M, FM-52xl, and FM-52 weld metals at 75%, 40%, 39% and 21% recrystallized, respectively. Weld metals containing strong carbide formers experienced higher recrystallization responses than those without due to precipitate–carbide interactions. All tested weld metals experienced drastic reductions in DDC response with increasing extent of recrystallization and decreasing average grain surface areas. DRX in STF specimens was observed to facilitate uniform plastic strain accumulation, lowering overall DDC susceptibility compared to non-recrystallized specimens. Full article

High-performance cutting materials are central to modern production engineering. Cemented carbides dominate industrial tooling, while polycrystalline boron nitride (PcBN) is established for hard turning and finishing nickel-based alloys. The associated tool manufacturing chains are energy- and effort-intensive, motivating approaches that reduce material losses and primary energy demand. This study quantifies energy consumption across the production of solid carbide cutting tools with a focus on near-net-shape green machining, its impact on subsequent grinding and material recirculation. It also quantifies energy consumption for regrinding PcBN cutting tools. Power measurements were recorded during green machining and tool grinding of cylindrical versus pre-contoured (green-machined) blanks, including coolant units for the carbide tools during operation. Tool performance of the carbide tools was assessed via milling tests in 42CrMo4; PcBN reground tools were evaluated in Inconel 718. In the process chain of carbide tool production, specific energy decreased from 6.98 to 6.36 kWh/kg (−8.88%) despite +0.461 kWh/kg for green machining; direct recirculation of green-machined material saved an additional 5.861 kWh/kg. Reground PcBN inserts achieved comparable tool life to new tools while reducing energy by ≈85% per insert. The dominant levers for energy reduction are shorter grinding times in the presence of high machine and coolant base loads and systematic regrinding of high-embodied-energy tools. Full article

Ice adhesion on exposed structures remains a major operational challenge, motivating the search for passive, material-based anti-icing strategies. Molecular dynamics offers a controlled way to investigate ice–surface interactions beyond the limits of experimental setups. In this work, we develop a simulation framework to model the impact of solid hexagonal ice droplets on metallic substrates. Ice impacts are simulated across a range of velocities (10–120 m/s), temperatures (120–250 K), and face-centred cubic surface materials (gold, copper, silver, aluminum, and nickel). Using LAMMPS, mW water force-field, EAM/Alloy metal potentials, and Lennard-Jones water–surface interactions, we quantify phase evolution through angular order parameter and quasi-liquid layer measurements, complemented by the CHILL+ algorithm in OVITO. By isolating all external factors, we show that melting increases with velocity and temperature and correlates with substrate properties: metals with high thermal diffusivity and low Young’s modulus tend to decrease post-collision ice melting. The ratio of the former to the latter, a derived index of merit Υ, significantly correlates with melting percentage and identifies silver as the most effective anti-ice material examined. Statistical analyses strongly suggest that these surface properties influence interfacial melting, supporting the use of this modelling framework for screening and designing anti-icing materials. Full article

Efficient joining of hard metals to steels is crucial for supporting sustainable manufacturing under emissions strategies to minimize CO₂. CoNiCrFeCu high-entropy alloy containing scandium (Sc) was designed as a filler for laser braze-welding of WC-Co and steel. The designed compositions with different Sc levels were melted and cast in a high-vacuum non-consumable arc furnace. The results showed that the as-cast microstructure was a complex mixture of a networked Ni₂Si, elongated Cr-Fe-Co solid-solution phase, and Fe-Ni-Co-Cu solid-solution phase. Scandium was shown to have formed compounds with nickel/cobalt and copper. The TG-DSC analysis confirmed that the melting points of the designed compositions were between 973.7 °C and 981.5 °C. The maximum spreading area of the CoNiCrFeCu-0.9Sc composition on AISI 1045 steel was 64.83 mm², and on the WC-Co cermet it was 78.63 mm². The interface between the fusion zone and AISI 1045 steel exhibited an epitaxial growth of dendrites from the steel base metal. The interface between WC-Co and the fusion zone exhibited a partial penetration of brazing filler into the Co matrix, forming a metallurgical bonding between the dissimilar materials. Sc, as an alloying element in the filler metal, enhanced the bond formation because it decreased the solidus temperature and increased wetting. Full article

Electronic waste (e-waste) offers a sustainable pathway for recovering critical metals, yet its heterogeneous composition complicates the design of advanced alloys. This work applies a computational approach to design multicomponent superalloys from e-waste, using Thermo-Calc to predict phase stability and microstructural evolution. Nickel-based alloys alloyed with Cu–Sn–Pb fractions were modeled, revealing improved ductility through phase refinement and suppression of graphite formation. Experimental validation with SEM and XRD confirmed the computational predictions. This study demonstrates the potential of integrating computational thermodynamics with e-waste recycling to develop high-performance superalloys, advancing both sustainability and material innovation. Full article

GH3039 nickel-based alloy, as a key material for thermocouple protection tubes, is susceptible to wear and oxidation failure in high-temperature kiln environment. To address this, boronized, chromized and borochromized coatings were prepared on GH3039 substrate, and the friction-wear properties and high-temperature oxidation resistance of both the substrate and the coatings were systematically characterized. The results show that the borochromized coating, benefiting from the synergistic effect of its relatively high surface hardness and the boric acid lubricating film formed during the wear process, reduces the wear rate by 84.07% (to 1.44 × 10⁻⁵ mm³·N⁻¹·m⁻¹). Meanwhile, it exhibits the optimal oxidation resistance due to its dense Cr-rich layer, which can inhibit oxygen diffusion and supply chromium for protective Cr₂O₃ film. After 100 h of oxidation at 950 °C, its oxidation weight gain is reduced by 78.68% compared with the boronized sample (to 1.20 mg/cm²). Full article

Nickel-based superalloy GH3625 is widely used in extreme environments due to its exceptional high-temperature strength and corrosion resistance; however, optimizing its comprehensive performance through precise microstructural control remains a critical challenge. In this study, the effect of withdrawal rate (10–200 μm/s) on the microstructural evolution, mechanical properties, and corrosion resistance of GH3625 alloy was investigated using a liquid-metal-cooled directional solidification system. The microstructural characteristics, elemental segregation, and phase distributions were systematically analyzed via OM, SEM, and EDS, followed by uniaxial tensile and electrochemical polarization tests. The results show that with increasing withdrawal rate, the solid–liquid interface morphology evolves from cellular to cellular-dendritic and finally to fully dendritic. Correspondingly, the primary dendrite arm spacing decreases from 270.4 μm to 100.2 μm, and the secondary dendrite arm spacing decreases from 66.5 μm to 12.3 μm. The area fraction of the detrimental Laves phase first decreases and then increases, reaching a minimum at 100 μm/s. Correspondingly, the yield strength increases from 282 MPa to 409 MPa, and the corrosion resistance is optimized at 100 μm/s. The microstructure–property relationships are discussed based on second-phase strengthening theory and microstructural refinement. This study provides a theoretical basis and practical process windows for optimizing directional solidification parameters to achieve enhanced mechanical and corrosion performance in GH3625 alloy. Full article

This article presents a review of current trends in the development of protective coatings for TiAl alloys. These materials have been indicated as potential replacements for nickel-based alloys for several decades; however, many problems related to their application have not yet been solved, such as low resistance to oxidation and high-temperature corrosion, limited wear and erosion resistance, as well as susceptibility to microstructural changes under demanding conditions. Research in this area has been conducted for many years; nevertheless, new concepts and types of coatings are constantly being developed, particularly for third- and fourth-generation TiAl alloys. This article presents a review and classification of protective coatings used for TiAl alloys, with particular emphasis on research results published in the scientific literature of the last decade. In addition to a literature review concerning coating types and applied technologies, new trends and concepts in this field proposed by the co-authors will also be presented. Full article

Stellite alloys are widely used in the aerospace field owing to their excellent high-temperature strength and thermal fatigue resistance. However, with the rapid development of the aerospace industry, there is an urgent demand to further enhance the mechanical properties and thermal fatigue resistance of Stellite alloys. In the present study, we prepared a conventional CoCrW alloy (classified as a Stellite alloy) and a novel CoCrWAlNi alloy, which was formulated by introducing aluminum and nickel into the CoCrW matrix, using the direct laser deposition technique. Their microstructural characteristics, mechanical properties, and thermal fatigue performance were systematically investigated. The results indicated that the additions of aluminum and nickel contribute to stabilizing the γ-Co phase. Compared with the CoCrW alloy, the CoCrWAlNi alloy exhibited higher elongation at fracture. In situ observation was employed to study the initiation and propagation of thermal fatigue cracks. Meanwhile, the effects of oxidation on thermal fatigue resistance were analyzed through experimental tests and theoretical calculations based on the Huntz model. Finally, an optimized thermal fatigue mechanism tailored for cobalt-based alloys was established, which yields deeper insights into the failure mechanisms of these alloys under complex thermal-cycling fatigue conditions. Full article