Search Results (286)

To enhance the operational damage resistance of hydraulic machinery, this study employed laser cladding technology to fabricate a Co_37.4Cr₃₀Ni₂₀Al₅Ti₅Nb_2.6 high-entropy alloy coating on 04Cr13Ni5Mo substrate. The influence of laser power on the microstructure and properties of the coating was systematically investigated. Based on preliminary research, the friction-wear performance and cavitation erosion behavior of the coatings prepared at 3000 W, 3200 W, and 3400 W were specifically examined. Results indicate that as the laser power increased from 3000 W to 3400 W, the microhardness of the coating gradually decreased from 345.3 HV_0.2. At 3000 W, the precipitation of trace strengthening phases significantly enhanced the mechanical properties. In wear tests under a 20 N load for 30 min, the wear rate of the coating prepared at 3000 W was 1.41 × 10⁻⁴ mm³/(N·m), which is 13.5% lower than that of the 3200 W coating (1.63 × 10⁻⁴ mm³/(N·m)) and 16.07% higher in wear resistance compared to the substrate. Cavitation erosion tests revealed that after 20 h of ultrasonic vibration, the mass loss of the 3000 W coating was only 2.35 mg, representing an 88.89% reduction compared to the substrate (21.15 mg), and significantly lower than that of the 3200 W (4.57 mg) and 3400 W (3.85 mg) coatings. This study demonstrates that precise control of laser power can effectively optimize the cavitation erosion resistance of high-entropy alloy coatings, providing technical support for their application in harsh environments. Full article

In this study, a multiphysics coupling numerical model was developed to investigate the thermal-fluid dynamics and microstructure evolution during the laser metal deposition of AlCoCrFeNi high-entropy alloy (HEA) coatings on 430 stainless steel substrates. The model integrated laser-powder interactions, temperature-dependent material properties, and the coupled effects of buoyancy and Marangoni convection on melt pool dynamics. The simulation results were compared with experimental data to validate the model’s effectiveness. The simulations revealed a strong bidirectional coupling between temperature and flow fields in the molten pool: the temperature distribution governed surface tension gradients that drove Marangoni convection patterns, while the resulting fluid motion dominated heat redistribution and pool morphology. Initially, the Peclet number (Pe_T) remained below 5, indicating conduction-controlled heat transfer with a hemispherical melt pool. As the process progressed, Pe_T exceeded 50 at maximum flow velocities of 2.31 mm/s, transitioning the pool from a circular to an elliptical geometry with peak temperatures reaching 2850 K, where Marangoni convection became the primary heat transfer mechanism. Solidification parameter distributions (G and R) were computed and quantitatively correlated with scanning electron microscopy (SEM)-observed microstructures to elucidate the columnar-to-equiaxed transition (CET). X-ray diffraction (XRD) analysis identified body-centered cubic (BCC), face-centered cubic (FCC), and ordered B2 phases within the coating. The resulting hierarchical microstructure, transitioning from fine equiaxed surface grains to coarse columnar interfacial grains, synergistically enhanced surface properties and established robust metallurgical bonding with the substrate. Full article

This study fabricated six types of NiCr–Cr₃C₂ composite coatings using high-velocity oxygen fuel (HVOF) spraying and systematically evaluated their tribological behavior at 350 °C and 500 °C, along with their electrochemical corrosion performance in 3.5 wt.% NaCl solution. The objective was to elucidate how compositional design regulates the coatings’ microstructure, mechanical properties, and service performance. Results indicate that the 75NiCr–25Cr₃C₂ coating (C) formed a stable oxide film under both temperatures, exhibiting oxidation-dominated wear and the lowest friction coefficient and wear rate. When the temperature increased from 350 °C to 500 °C, the wear rates of coatings C, B, E, and F decreased significantly. Notably, coatings E and F, which contained CoCrFeNiMo high-entropy alloy, showed more than a 50% reduction in wear rate, demonstrating the contribution of the high-entropy phase to high-temperature wear resistance. At 350 °C, coatings B, D, E, and F experienced primarily abrasive wear; at 500 °C, however, E and F shifted to oxidative wear as the dominant mechanism, leading to a marked improvement in wear resistance. Electrochemical measurements revealed that coating E exhibited the best corrosion resistance, while the NiCr coating (A) performed the worst. The findings highlight that optimizing Cr₃C₂ content and incorporating high-entropy alloy elements can synergistically enhance both high-temperature tribological properties and corrosion resistance. Full article

High-entropy alloy (HEA) thin films have attracted considerable attention owing to their multi-element synergistic effects, high stability, tunable electronic structure, and low-cost potential. In this study, an FeCoNiMoCu HEA thin-film electrode was successfully fabricated via coating and vacuum sintering techniques, using equiatomic Fe, Co, Ni, Mo, and Cu powders as precursors. The crystal structure, surface morphology, elemental composition/distribution, and chemical states of the FeCoNiMoCu HEA thin-film electrode were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The hydrogen evolution reaction (HER) performance of the electrode was evaluated in four different electrolyte systems. Additionally, the influence of electrolyte temperature on HER activity was investigated, with the corresponding activation energy (E_a) calculated for each tested system. Results demonstrate that the FeCoNiMoCu HEA thin-film electrode exhibits outstanding HER performance across multiple electrolyte systems. Compared with conventional HER catalysts, this FeCoNiMoCu thin-film electrode achieves a balance between high catalytic activity and broad electrolyte compatibility, filling the research gap in HEA thin-film catalysts with superior performance in various complex electrolyte environments and providing a new reference for the development of low-cost, high-stability HER catalysts for practical applications. Full article

High-entropy alloy (HEA) coatings have attracted significant attention in the nuclear power field due to their exceptional properties, showing great potential for accident-tolerant fuel (ATF) applications. In this study, novel AlCrFeMoZr HEA coatings with a near-equal molar ratio were successfully fabricated via magnetron sputtering at different bias voltages (−50 V, −100 V, and −150 V). The influence of bias voltage on the microstructure and mechanical properties of the coatings was systematically investigated. The results reveal that all HEA coatings exhibit a body-centered cubic structure with a (110) preferential orientation. As the bias voltage increased, the Al content in the HEA coating decreased, and the microstructure coarsened. The microhardness and friction and wear test results demonstrate that an HEA coating deposited at −100 V exhibited optimal mechanical properties owing to its good balance between hardness and toughness, leading to an improved tribological performance. Furthermore, a high-temperature water vapor oxidation experiment was conducted at 1200 °C in order to preliminarily study the differences in the anti-oxidation behavior of the new composition, an AlCrFeMoZr HEA coating, when deposited at various biases. Full article

In this study, the effects of different Mn content and heat treatment on the microstructure and properties of CoCrFeNiTi coatings by laser cladding technology were investigated. Scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction were used to analyze the structure and composition. The hardness and wear resistance were tested by a microhardness tester and a friction-wear tester. The results show that there are many intermetallic compounds rich in Ti and Ni between the grains. As the Mn content increases, the coating gradually transitions from a dual-phase structure of BCC and FCC to a single FCC structure. The hardness of the coating decreases gradually with the increase in Mn content due to the change in the phase structure, while the friction coefficient decreases slightly at first and then increases significantly. The main wear mechanisms of the coating are adhesive wear and abrasive wear. After heat treatment at 600 °C, petal-like Laves precipitates appear. The average microhardness of CoCrFeNiTi coatings after heat treatment is lower than before treatment, and the friction coefficient is higher than before treatment. The average microhardness of the coating increases slightly with the increase in the treatment temperature. The average friction coefficient of the coating obtained after heat treatment at 600 °C is only 0.5941 because of its uniform microstructure. Therefore, it is reduced by approximately 15% compared with the base metal. Full article

Surface coatings have proven highly effective in addressing the critical challenges of friction, wear, and corrosion on steel substrates, which are responsible for over 80% of mechanical failures in industrial applications. Recent research highlights that advanced coatings—such as ceramic carbides/nitrides, high-entropy alloys, and metal-matrix composites—significantly enhance hardness, wear resistance, and environmental durability through mechanisms including protective oxide film formation, solid lubrication, and microstructural refinement. Moreover, these coatings exhibit robust performance under combined tribological-corrosive (tribocorrosion) conditions, where synergistic interactions often accelerate material degradation. Key developments include multilayer and composite architectures that balance hardness with toughness, self-lubricating coatings capable of in situ lubricant release, and active or self-healing systems for sustained corrosion inhibition. Despite these advances, challenges remain in predicting coating lifetime under multifield service conditions and optimizing interfacial adhesion to prevent delamination. Future efforts should prioritize multifunctional coating designs, improved tribocorrosion models, and the integration of sustainable materials and AI-driven process optimization. This review consolidates these insights to support the development of next-generation coatings for extending the service life of steel components across demanding sectors such as marine, aerospace, and energy systems. Full article

This study employed atmospheric plasma spraying (APS) technology to successfully fabricate CoCrFeNiMo high-entropy alloy (HEA) coatings under varying spraying currents and systematically investigated the effects of the spraying current on the microstructure, mechanical properties, and tribological behavior of the coatings. Results showed that the material composition remained consistent across different current levels, primarily consisting of face-centered cubic (FCC) solid solution phases, FeCr₂O₄ spinel phases, and Cr-rich FCC1 phases. The FCC matrix was dispersed with spherical Cr oxide particles smaller than 30 nm in diameter, which significantly enhanced the strength of the coatings. As spraying current increased, both porosity and microhardness exhibited a non-monotonic trend—initial optimization followed by deterioration. At 500 A spraying current, the coating achieved optimal performance, with the lowest porosity (0.42%) and highest microhardness (569.8 HV). Correspondingly, this condition also yielded the best wear resistance, with stable friction coefficients and wear rates reaching 0.49 and 6.91 × 10⁻⁵ mm³/N m, respectively. Abrasion surface analysis revealed that excessively low or high currents triggered distinct wear mechanisms leading to reduced wear resistance. Full article

FeCoNiCuAl high-entropy alloys exhibit remarkable mechanical properties; nevertheless, these materials struggle to withstand harsh environments because of their insufficient resistance to wear and corrosion. The addition of Si can significantly enhance the alloy’s high-temperature performance, hardness, and wear resistance, thereby making it more suitable for applications in high-temperature or corrosive environments. To overcome these drawbacks, this research investigates how varying Si content affects the microstructure and properties of FeCoNiCuAl coatings. Composite coatings of FeCoNiCuAlSi_x (x = 0, 0.5, 1.0, 1.5, 2.0) were fabricated on 65 Mn substrates using laser cladding. Various testing methods, including metallographic microscopy, Vickers hardness testing, friction and wear testing, and electrochemical analysis, were employed to examine the phase structure, microstructure, and hardness of the coating. It is observed that the FeCoNiCuAl coating begins with a uniform FCC phase structure. However, as the Si content increases, a phase transformation to the BCC structure occurs. The microstructure is primarily composed of isometric crystals and dendrites that become finer and more compact with higher Si content. For the FeCoNiCuAlSi_2.0 coating, the microhardness reaches 581.05 HV_0.2. Additionally, wear resistance shows a positive correlation with Si content. Electrochemical testing in NS4 solution shows that the corrosion potential of the coating increases from −0.471 V for FeCoNiCuAl to −0.344 V for FeCoNiCuAlSi_2.0, while the corrosion current density decreases from 1.566 × 10⁻⁶ A/cm² to 4.073 × 10⁻⁶ A/cm². These results indicate that Si addition plays a crucial role in enhancing the mechanical properties and corrosion resistance of FeCoNiCuAl coatings, making them more suitable for high-performance applications in extreme environments. Full article

Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and process parameters enable composite coatings with a combination of high hardness and self-lubrication properties, while post-treatments like laser melting or corrosion inhibitors extend salt spray corrosion resistance. Titanium alloys benefit from MAO coatings with exceptional interfacial bonding strength and mechanical performance, making them ideal for biomedical implants and aerospace components. Notably, dense ceramic oxide films grown in situ via MAO on high-entropy alloys (HEAs) triple surface hardness and enhance wear/corrosion resistance. However, MAO applications on steel require pretreatments like aluminizing, thermal spraying, or ion plating. Current challenges include coating uniformity control, efficiency for complex geometries, and long-term stability. Future research focuses on multifunctional coatings (self-healing, antibacterial) and eco-friendly electrolyte systems to expand engineering applications. Full article

To address the synergistic degradation mechanisms in engineering service environments, we propose a boron microalloying strategy to enhance the multifunctional surface performance of AlCoCrFeNiMo-based high-entropy alloys. AlCoCrFeNiMoTiBx coatings (x = 0, 0.5, 1, and 1.5) were fabricated on Q235 steel substrates using laser cladding. The microstructure of the coatings was characterized using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), while their wear and corrosion resistance were evaluated through tribological and electrochemical tests. The key findings indicate that boron addition preserves the original body-centered cubic (BCC) and σ phases in the coating while promoting the in situ formation of TiB₂, leading to lattice distortion. With increasing B content, the BCC phase becomes refined, and both the fraction and size of TiB₂ particles increase. Boron incorporation improves the coating’s microhardness and wear resistance, with the highest wear resistance achieved at x = 1, where abrasive and oxidative wear predominate. At lower content (x = 0.5), B enhances the stability of the passive film and thereby improves corrosion resistance. In contrast, excessive formation of large TiB₂ particles introduces defects into the passive film, accelerating its degradation. Full article

In order to improve the wear resistance of H13 hot work die steel, high-entropy alloy composite coatings were prepared by laser cladding technology and were subsequently subjected to ultrasonic rolling. The results showed that after ultrasonic rolling, the phases of the coatings still consisted of BCC phase, TiO₂, ZrO₂, and B₄C. The microstructure of the coatings was the equiaxed grain; however, the grain size decreased compared with that of the laser cladding coating. Under the combined effects of fine grain strengthening and work hardening, the hardness and wear resistance of the coatings treated by ultrasonic rolling were significantly improved. Among them, the coating at 0.09 MPa exhibited the best mechanical properties, with a hardness increase of 18.7% compared with the laser cladding coating and 534.9% compared with H13. At room temperature, compared with the laser cladding coating and H13, the wear rates of the coating at 0.09 MPa were reduced by 27% and 91%, respectively. At high temperatures (350 °C, 450 °C, and 550 °C), the wear rates of the coating at 0.09 MPa were reduced by 19%, 13%, and 9% compared with the laser cladding coating, and reduced by 89%, 88%, and 87% compared with H13. Full article

Aircraft engine turbine discs operate under extreme conditions that limit their service life. Laser cladding of AlCoCrFeNi HEA coatings presents a viable solution to enhance their durability. This study optimizes the laser cladding process parameters—specifically, laser power, scanning speed, and powder feed rate—using the Taguchi method in conjunction with grey relational analysis. The optimal parameter set (1450 W, 480 mm/min, 4 r/min) resulted in a coating with a width of 2.93 mm, a height of 1.20 mm, a dilution rate of 22.6%, and a hardness of 532 HV. The optimized process significantly improved hardness by approximately 15% while reducing dilution and elemental segregation in comparison to the initial parameters. This research illustrates the effectiveness of multi-objective optimization in enhancing coating performance, providing a practical approach for the surface strengthening of critical components, such as turbine discs in aircraft engines, under extreme conditions. Full article

In order to enhance the performance of 20# steel, this study successfully fabricated AlCoCrFeNi high-entropy alloy coatings with different WC contents (x = 0, 10, 20, 30 wt%) on its surface using plasma cladding technology. The effects of WC content on the microstructure, mechanical properties, and corrosion resistance of the coatings were systematically investigated. The results indicate that without WC addition, the coating consists of a dual-phase structure comprising BCC and FCC phases. With the incorporation of WC, the FCC phase disappears, and the coating evolves into a composite structure based on the BCC matrix, embedded with multiple carbide phases such as W₂C, M₇C₃, M_xC_γ, and Co₆W₆C. These carbides are predominantly distributed along grain boundaries. As the WC content increases, significant grain refinement occurs and the volume fraction of carbides rises. The coating exhibits a mixed microstructure of equiaxed and columnar crystals, with excellent metallurgical bonding to the substrate. The microhardness of the coating increases markedly with higher WC content; however, the rate of enhancement slows when WC exceeds 20 wt%. The hardness of 1066.36 HV is achieved at 30 wt% WC. Wear test results show that both the friction coefficient and wear rate first decrease and then increase with increasing WC content. The optimal wear resistance is observed at 20 wt% WC, with a friction coefficient of 0.549 and a wear mass loss of only 0.25 mg, representing an approximately 40% reduction compared to the WC-free coating. Electrochemical tests demonstrate that the coating with 20 wt% WC facilitates the formation of a dense and stable passive film in NaCl solution, effectively inhibiting Cl⁻ ion penetration. This coating exhibits the best corrosion resistance, characterized by the lowest corrosion current density of 1.349 × 10⁻⁶ A·cm⁻² and the highest passive film resistance of 2764 Ω·cm². 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