Search Results (297)

To promote the high-value recycling of machining return materials from powder metallurgy (P/M) FGH95 superalloy production, a vacuum induction melting refining process was developed to achieve gas impurity purification and compositional control. Cylindrical solid returns obtained from wire-cut electrical discharge machining were used as feedstock, and the effects of refining temperature (1550–1650 °C) and holding time (10–30 min) on impurity removal and element stability were systematically investigated. For each condition, three repeated melts were performed, and the average gas contents (mean ± SD) were evaluated by inert-gas fusion analysis. Results show that at 1650 °C, O decreased from 8 ppm to 6 ppm, N decreased from 6 ppm to 3 ppm, while H remained below the detection limit (<1 ppm). Prolonged refining caused slight compositional deviations, with Cr exhibiting measurable volatilization, whereas Al and Ti showed minor increases (<0.06 wt.%). A kinetic model describing O removal was established, yielding an apparent activation energy of 128 kJ·mol⁻¹, confirming diffusion-controlled deoxidation behavior. The optimal refining condition—1650 °C for 10 min—achieved efficient removal of O and H while maintaining alloy compositional stability. This study provides both a practical refining route and a kinetic basis for the purification and reuse of machining returns in nickel-based P/M superalloys, contributing to cost reduction and sustainable manufacturing. Full article

Yttria-stabilized zirconia(YSZ) was introduced into the Al₂O₃-TiO₂-CeO₂ coating prepared by plasma spraying to improve the wear resistance of the coating and prolong the service life of the weathering steel. The nano-agglomerated powder was prepared by mechanical ball milling and spray-drying technology, powder was sprayed on the surface of Q355 steel substrate by atmospheric plasma sparing (APS), the Al₂O₃-TiO₂-CeO₂/YSZ composite coating was prepared, and the effects of YSZ on the phase, microstructure, and tribological properties of the composite coating were studied. The results show that nano-agglomerated powders with micron size (average size 55 μm) can be prepared by spray-drying technology, and after high-temperature sintering, the nano-agglomerated powders are denser and form the α-Al₂O₃ phase. The composite coating prepared by plasma spraying has a bimodal structure, and after adding YSZ, the phases in the coating are mainly α-Al₂O₃, γ-Al₂O₃, and t-ZrO₂, the grain size is fine, and the porosity is reduced. The specific wear rate is only 4.4 × 10⁻⁵ mm³ N⁻¹·m⁻¹, the relative wear resistance is 6.3 times higher than that of the substrate, and the wear mechanism of the coating is mainly slight adhesive wear and abrasive wear, which shows excellent friction and wear properties at room temperature. Full article

The low-temperature impact properties of high-heat-input steels, particularly low-carbon Nb–Ti steel, are significantly influenced by the coarse-grained heat-affected zone (CGHAZ) in welded joints. The microstructure predominantly consists of granular bainitic ferrite (GBF), ferrite side plate (FSP), degenerate pearlite (DP), coarse plate-like ferrite (PF), and limited acicular ferrite (AF). This study investigates the effect of lanthanum (La) addition to Nb–Ti steel, leading to the formation of composite inclusions with a LaAlO₃·TiN core surrounded by MnS/MnC precipitates. Unlike conventional Al₂O₃·MnS inclusions in Nb–Ti steel, these La-modified inclusions promote enhanced AF nucleation. This not only refines prior austenite grains but also reduces detrimental microstructural constituents such as GBF and FSP. As a result, the impact energy at −40 °C significantly improves from 23 J (Nb–Ti steel) to 137 J (Nb–Ti–La steel). Moreover, the inclusions exhibit an increase in size but a decrease in number density. The Nb–Ti–La variant demonstrates a higher AF volume fraction and increased AF density within the CGHAZ. The refined grain structure, along with an increased proportion of high-angle grain boundaries, effectively impedes secondary crack propagation. These microstructural modifications contribute to a substantial improvement in the low-temperature impact toughness of welded joints. Full article

Titanium alloys are widely employed in structural and electrochemical applications owing to their excellent mechanical properties and inherent corrosion resistance. However, their stability in harsh acidic environments, such as those encountered in energy storage systems, remains a critical issue. In this study, composite ceramic coatings were synthesized on a Ti6Al4V alloy using plasma electrolytic oxidation (PEO) in silicate-, phosphate-, and sulfate-based electrolytes, with and without the addition of α-alumina nanoparticles. The resulting coatings were comprehensively characterized to assess their surface morphology, chemical and phase compositions, and corrosion performance. Thus, the corrosion current density decreased from 9.7 × 10⁴ for bare Ti6Al4V to 143 nA/cm² for the coating fabricated in phosphate electrolyte with alumina nanoparticles, while the corrosion potential shifted anodically from –0.68 to +0.49 V vs. silver chloride electrode in 5 M H₂SO₄. Among the tested electrolytes, coatings produced in the phosphate-based electrolyte with Al₂O₃ showed the highest polarization resistance (113 kΩ·cm²), outperforming those fabricated in silicate- (71.6 kΩ·cm²) and sulfate-based (89.0 kΩ·cm²) systems. The composite coatings exhibited a multiphase structure with reduced surface porosity and the incorporation of crystalline oxide phases. Notably, titania–alumina nanoparticle composites demonstrated significantly enhanced corrosion resistance. These findings confirm that PEO-derived composite coatings provide an effective surface engineering strategy for enhancing the stability of the Ti6Al4V alloy in aggressive acidic environments relevant to advanced electrochemical systems. Full article

Carbon fibre reinforced polymer (CFRP) is a composite material known for its light weight and exceptional durability, composed of carbon fibres within a polymer matrix. Despite its high cost, CFRP is favoured for its outstanding strength-to-weight ratio and rigidity. It is widely used in the aerospace industry and ship superstructures, among others. These components often rub against different materials in various structural and mechanical assemblies. These interactions typically occur where metallic fasteners, bearings, hinges, and sliding components interface with CFRP parts causing, for example, fretting wear. The main novelty of the present study consists of a systematic comparison of titanium (Ti6Al4V) and aluminium (AA2024-T6) alloy spheres under identical test conditions, evaluating how each material interacts with different CFRP configurations. CFRP was tested against titanium and aluminium alloy spheres as counterbodies under reciprocating sliding conditions. Different contact conditions (applied loads) were used for tribotests. The wear volume and coefficient of friction were determined, as well as the wear mechanisms. Different analytical techniques were employed, such as profilometry, optical microscopy (OM), and scanning electron microscopy (SEM/EDS), to characterise the wear tracks. It was possible to determine the coefficient of friction as well as the wear rate on both CFRP specimens and their respective counterbodies. It was found that the coefficient of friction (CoF) depends on load, fibre orientation, and counterbody material, ranging from 0.14 to 0.29. The lowest wear rate coefficient was observed for CFRP sliding against titanium alloy in the layer configuration, at 1.48 × 10⁻¹³ mm³/N·m. In contrast, aluminium alloy counterbodies experienced significantly higher wear, with a maximum wear rate of 6.88 × 10⁻⁵ mm³/N·m. Wear volume increased with load across all conditions and was highest for the CFRP cross-section against aluminium alloy. Full article

In this study, the electrochemical corrosion behavior of TiAlZrTaNb nitride thin films deposited on 304 stainless steel substrates was investigated. The thin films were synthesized using high-power impulse magnetron sputtering (HiPIMS) and are classified as high-entropy alloys (HEAs). The microstructure, morphology, and chemical composition of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), respectively. Corrosion resistance was evaluated through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, employing tap water, acetic acid, and citric acid solutions at room temperature as electrolytes. The results demonstrated that the TiAlZrTaNbN coating exhibits a dense and homogeneous structure with a uniform elemental distribution. XRD analysis revealed the presence of face-centered cubic (FCC) crystalline phases, which significantly contribute to the coating’s corrosion resistance. Furthermore, the coating displayed exceptional corrosion performance in both acetic acid and citric acid electrolytes—simulating food environments with a pH ≤ 4.5—as revealed by a substantial reduction in corrosion current density and a positive shift in corrosion potential. These findings provide valuable insights into the properties of TiAlZrTaNbN coatings and underscore their potential for enhancing the durability of mechanical components employed in the food industry. Full article

By integrating cathodic arc evaporation (CAE) with magnetron sputtering (MS) or high-power impulse magnetron sputtering (HiPIMS), hard coatings with diverse multicomponent compositions can be fabricated. Depending on the deposition conditions, the coatings with nano-composite or nano-multilayered microstructures are produced. During the mixing deposition conditions, nano-composite coatings are fabricated, which can be tailored to possess combining properties of super hardness, low friction coefficient, and excellent thermal/chemical stability. For the deposition with larger rotating periods, layer-by-layer deposition was observed. By the nano-multilayered coating design, superior mechanical properties (hardness ≥ 35 GPa), modulated residual stresses, and enhanced high-temperature properties can be obtained. In addition, lubricious elements, low friction (friction coefficient < 0.4), and low wear (<10⁻⁵ mm³/N∙m) both at ambient temperature and high temperature can be realized. Among these coatings, some have been specifically designed to achieve outstanding cutting performance in high-speed cutting applications. Several nitride and oxide hard coatings, such as AlTiN, TiAlN/TiSiN, AlCrN/Cu, and AlCrO, were deposited using a hybrid industrial physical vapor deposition (PVD) coating system. The microstructure, mechanical properties, and cutting performance of these coatings will be discussed. Full article

In order to enhance the heat dissipation of a chip, this work investigates the enhancement of the thermal homogenization effect of a ceramic substrate with a high-thermal-conductivity graphene material to improve the interfacial heat transfer performance. AgCuTi-activated brazing material is used to connect the graphene film/AlN. The mechanism of the influence of brazing temperatures on the microstructure and thermal conductivity of joints is discussed. The thermal conductivity of the graphene/AlN double layer composite brazed at 890 °C for 10 min holding time was the highest at 482.3 W m⁻¹ K⁻¹. This study provides a new solution for the application of AlN ceramics in high-heat-flow scenarios. Full article

With the rapid development of advanced machining technologies such as high-speed cutting, dry cutting, and ultra-precision cutting, as well as the widespread application of various difficult-to-machine materials, the surface degradation problems such as wear, oxidation, and delamination faced by tools in the service process have become increasingly prominent, seriously restricting the performance and service life of tools. Nanocoatings, with their distinct nano-effects, provide superior hardness, thermal stability, and tribological properties, making them an effective solution for cutting tools in increasingly demanding working environments. For example, the hardness of the CrAlN/TiSiN nano-multilayer coating can reach 41.59 GPa, which is much higher than that of a single CrAlN coating (34.5–35.8 GPa). This paper summarizes the most common nanocoating material design, coating deposition technologies, performance evaluation indicators, and characterization methods currently used in cutting tools. It also discusses how to improve nanocoating performance using modulation analysis of element content, coating composition, geometric structure, and coating thickness. Finally, this paper considers the future development of nanocoatings for cutting tools in light of recent research hotspots. Full article

The objective of this study was to investigate the physicochemical properties of hybrid coatings with titanium nitride and boron nitride nanoparticles deposited on the TiAlV medical alloy via the sol–gel process. The developed layers were intended to impart bactericidal properties and provide protection against surgical abrasions during the implantation procedure. This study focused on evaluating the microstructure (SEM + EDS), structure (XRD, FTIR), and surface properties, including wettability, surface free energy, and roughness of the synthesized layers. Our results confirmed that it was feasible to produce hybrid layers with various microstructures and diverse layer morphologies. The FTIR and XRD structural analyses confirmed the presence of an organosilicon matrix incorporating the two aforementioned types of ceramic particles. Full article

Drilling-induced damage in fiber-reinforced polymer composite materials was measured excavating four laminates, basalt (B₁₄), glass (G₁₄) and their two sandwich type hybrids (B₄G₆B₄, G₄B₆G₄), with 6 mm twist drills at 1520 revolutions per minute and 0.10 mm rev⁻¹ under dry running with an uncoated high-speed steel (HSS-R), grind-coated high-speed steel (HSS-G) or physical vapor deposition-coated (high-speed steel coated with Titanium Nitride (TiN) and Titanium Aluminum Nitride (TiAlN)) drill bits. The hybrid sheets were deliberately incorporated to clarify how alternating basalt–glass architectures redistribute interlaminar stresses during drilling, while the hard, low-friction TiN and TiAlN ceramic coatings enhance cutting performance by forming a heat-resistant tribological barrier that lowers tool–workpiece adhesion, reduces interface temperature, and thereby suppresses thrust-induced delamination. Replacement of an uncoated, grind-coated, high-speed-steel drill (HSS-G) with the latter coats lowered the mechanical and thermal loads substantially: mean thrust fell from 79–94 N to 24–30 N, and peak workpiece temperatures from 112 °C to 74 °C. Accordingly, entry/exit oversize fell from 2.5–4.7% to under 0.6% and, from the surface, the SEM image displayed clean fiber severance rather than pull-out and matrix smear. By analysis of variance (ANOVA), 92.7% of the variance of thrust and 86.6% of that of temperature could be accounted for by the drill-bit factor, thus confirming that the coatings overwhelm the laminate structure and hybrid stacking simply redistribute, but cannot overcome, the former influence. Regression models and an artificial neural network optimized via meta-heuristic optimization foretold thrust, temperature and delamination with an R² value of 0.94 or higher, providing an instant-screening device with which to explore industrial application. The work reveals TiAlN- and TiN-coated drills as financially competitive alternatives with which to achieve ±1% dimensional accuracy and minimum subsurface damage during multi-material composite machining. Full article

Titanium alloys are frequently subjected to surface treatments to enhance their biocompatibility and corrosion resistance in biological environments. Plasma electrolytic oxidation (PEO) is an environmentally friendly electrochemical technique capable of forming oxide layers characterized by high corrosion resistance, biocompatibility, and strong adhesion to the substrate. In this study, the PEO process was performed using a low-melting-point ternary eutectic electrolyte composed of Ca(NO₃)₂–NaNO₃–KNO₃ (41–17–42 wt.%) with the addition of ammonium dihydrogen phosphate (ADP). The use of this electrolyte system enables a reduction in the operating temperature from 280 to 160 °C. The effects of applied voltage from 200 to 400V, current frequency from 50 to 1000 Hz, and ADP concentrations of 0.1, 0.5, 1, 2, and 5 wt.% on the growth of titanium oxide composite coatings on a Ti-6Al-4V substrate were investigated. The incorporation of Ca and P was confirmed by phase and chemical composition analysis, while scanning electron microscopy (SEM) revealed a porous surface morphology typical of PEO coatings. Corrosion resistance in Hank’s solution, evaluated via Tafel plot fitting of potentiodynamic polarization curves, demonstrated a substantial improvement in electrochemical performance of the PEO-treated samples. The corrosion current decreased from 552 to 219 nA/cm², and the corrosion potential shifted from −102 to 793 mV vs. the Reference Hydrogen Electrode (RHE) compared to the uncoated alloy. These findings indicate optimal PEO processing parameters for producing composite oxide coatings on Ti-6Al-4V alloy surfaces with enhanced corrosion resistance and potential bioactivity, which are attributed to the incorporation of Ca and P into the coating structure. Full article

The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be interpreted through the trace and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analyses of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ −6.8 to +0.7‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved in composition. Mineralized quartz displays marked enrichment in As (raw mean = 2854 ± 6821 ppm; filtered mean = 70 ± 93 ppm; one spot 16,775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (<0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but variable LREE enrichment ((La/Yb)_n ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures indicate chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, less fractionated REE profiles, higher Ti/Al, and weaker Eu anomalies. A composite exploration toolkit emerges: As > 700 ppm, As/Sb > 25, Ti/Al < 0.005, Ge/Si > 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably identify ore-bearing zones when integrated with δ¹⁸O data and fluid-inclusion microthermometry from earlier studies on the same vein system. This study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering an applicable model for vectoring mineralization in analogous settings worldwide. Full article

To promote the optimization of the anti-friction and anti-wear behavior of lightweight TiAl alloys, γ-TiAl-10 wt.% Ag self-lubricating composites were fabricated, and their mechanical and tribological properties were tested. The results showed that the silver in TiAl-10 wt.% Ag slightly reduced its mechanical properties compared with those of pure TiAl alloys. A silver-enriched lubrication film formed on a wear scar, which was helpful in improving the friction and wear behavior. It was found that a large amount of silver gathered at a wear scar, gradually spread out under the action of the sliding friction force, and then increased the silver distribution areas on the wear scar, leading to the good formation of a silver-rich film. Furthermore, an identification model was established to calculate the specific area η of the silver film. A quantitative relationship indicated that an increase in the Ag distribution area improved the tribological behavior of γ-TiAl-10 wt.% Ag. When the specific area η of a silver-rich film was maintained at 44–51%, the small friction coefficient (almost 0.28) and wear rate (about 2.25 × 10⁻⁴ mm³·N⁻¹·m⁻¹) were well stabilized. This provides a new research method to improve the tribological performance of TiAl-Ag samples. Full article

Functionally graded materials (FGMs) are fabricated on Ti-6Al-4V alloy surfaces to improve insufficient surface hardness and wear resistance. Microstructure and mechanical properties and strengthening–toughening mechanisms of FGMs were investigated. The FGM cladding layer exhibits distinct gradient differentiation, demonstrating gradient variations in the nanoindentation hardness, wear resistance, and Al/V elemental composition. Molten pool dynamics analysis reveals that Marangoni convection drives Al/V elements toward the molten pool surface, forming compositional gradients. TiN-AlN eutectic structures generated on the FGM surface enhance wear resistance. Rapid solidification enables heterogeneous nucleation for grain refinement. The irregular wavy interface morphology strengthens interfacial bonding through mechanical interlocking, dispersing impact loads and suppressing crack propagation. FGMs exhibit excellent wear resistance and impact toughness compared with Ti-6Al-4V titanium alloy. The specific wear rate is 1.17 × 10⁻² mm³/(N·m), dynamic compressive strength reaches 1701.6 MPa, and impact absorption energy achieves 189.6 MJ/m³. This work provides theoretical guidance for the design of FGM strengthening of Ti-6Al-4V surfaces. Full article