Coatings

31 pages, 41126 KB

Open AccessArticle

An Experimental Study on Blade Surface De-Icing by Combined Methods of PCMS-PUR Coating and Electric Heating Under Saline Water Conditions

by Yuqi Zhang, Zheng Sun, Zhiyuan Liu, Yan Li and Jiaqi Liu

Coatings 2026, 16(7), 744; https://doi.org/10.3390/coatings16070744 (registering DOI) - 23 Jun 2026

Abstract

Offshore wind turbine blades in cold marine environments are exposed to low-temperature, high-humidity, and saline-droplet conditions, under which the melting behavior, interfacial sliding, and de-icing energy demand of saline ice differ from those of freshwater ice. Existing studies on combined phase-change coating–electrothermal de-icing [...] Read more.

Offshore wind turbine blades in cold marine environments are exposed to low-temperature, high-humidity, and saline-droplet conditions, under which the melting behavior, interfacial sliding, and de-icing energy demand of saline ice differ from those of freshwater ice. Existing studies on combined phase-change coating–electrothermal de-icing have mainly focused on freshwater icing. Here, a glass-fiber-reinforced polymer (GFRP) NACA0018 airfoil was tested in a recirculating low-temperature icing wind tunnel to evaluate an n-tetradecane phase-change microcapsule/polyurethane (PCMS-PUR) coating combined with electrothermal heating at a salinity of 3%. Operating parameters, including heat flux density (8, 10, and 12 kW/m²), ambient temperature (−5, −10, and −15 °C), and incoming wind speed (3, 6, and 9 m/s), were systematically varied under a constant water flow rate (60 mL/min) and spray pressure (0.3 MPa) to characterize the evolution of ice morphology, temperature response, and de-icing energy consumption. During electrothermal de-icing, saline ice was more prone to interfacial softening and lubricating meltwater-layer formation, resulting in a dominant whole-block sliding detachment mode rather than gradual local melting. The PCMS-PUR coating further promoted interfacial melting and advanced ice destabilization through latent-heat release and thermal buffering. When the heat flux density increased from 8 to 12 kW/m², the de-icing energy consumption of the uncoated and coated blades decreased by 45.08% and 42.53%, respectively. The maximum energy-saving efficiency of the combined system reached 16.27% at 9 m/s. These findings clarify the de-icing behavior and energy-saving potential of combined phase-change coating–electrothermal systems under saline icing and provide guidance for the design of low-energy de-icing systems for offshore wind turbine blades. Full article

(This article belongs to the Collection Feature Paper Collection for Topic Editors and Invited Scholars in Coatings)

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22 pages, 5201 KB

Open AccessArticle

Aqueous Extract of Ammodaucus leucotrichus L. as an Eco-Friendly Corrosion Inhibitor for Mild Steel Under Acid Pickling Conditions: Electrochemical, SEM/EDS, and DFT Study

by Otmane Kharbouch, Asmaa Oubihi, Omar Belhadj, Sara Cherrad, Musa A. Said, Elhachmia Ech-cihbi, Moussa Ouakki and Younes Chhiti

Coatings 2026, 16(7), 743; https://doi.org/10.3390/coatings16070743 (registering DOI) - 23 Jun 2026

Abstract

The aqueous seed extract of Ammodaucus leucotrichus Cosson & Durieu (AL-AE), a Saharan annual herb of the family Apiaceae, was evaluated for the first time as a green corrosion inhibitor for mild steel in 1.0 M hydrochloric acid. GC-MS analysis after [...] Read more.

The aqueous seed extract of Ammodaucus leucotrichus Cosson & Durieu (AL-AE), a Saharan annual herb of the family Apiaceae, was evaluated for the first time as a green corrosion inhibitor for mild steel in 1.0 M hydrochloric acid. GC-MS analysis after acetylation derivatization identified ten constituents representing 99.22% of the total detected area, with 17-pentatriacontene (47.69%), 2,4-di-tert-butylphenol (13.24%), and myo-inositol (8.62%) as the dominant species. Inhibition performance was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) over 25–100 ppm at 298–328 K. At 100 ppm and 298 K, AL-AE achieved 96.17% by EIS and 97.10% by PDP. Adsorption obeyed the Langmuir model with a standard free energy of adsorption of −38.2 kJ mol⁻¹, consistent with a mixed physisorption–chemisorption mechanism. SEM/EDS confirmed protective film formation, with surface oxygen dropping from 34.9 to 4.1 wt%. Density functional theory (DFT) calculations at the B97-3c/CPCM (water) level in ORCA 6.1 identified 2,4-di-tert-butylphenol as the most reactive constituent, while Fukui index analysis based on Mulliken population analysis located the preferential adsorption sites on each molecule. Full article

(This article belongs to the Special Issue Smart Surface Engineering and Coatings for Corrosion Mitigation)

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31 pages, 4697 KB

Open AccessReview

Environmental Aging Mechanisms and Their Impact on the Mechanical Performance of Fiber-Reinforced Polymer Composites: A Comprehensive Review

by Tengwen Feng, Run Wang, Bing Du, Hanlin Ran, Yun Bai, Jingwei Liu and Feifei Fang

Coatings 2026, 16(6), 742; https://doi.org/10.3390/coatings16060742 (registering DOI) - 22 Jun 2026

Abstract

Fiber-reinforced polymer (FRP) composites are extensively used in aerospace, civil engineering, and defense applications because of their low density, high specific strength, corrosion resistance, and structural design flexibility. However, prolonged exposure to hygrothermal conditions, ultraviolet (UV) radiation, and thermo-oxidative environments can progressively damage [...] Read more.

Fiber-reinforced polymer (FRP) composites are extensively used in aerospace, civil engineering, and defense applications because of their low density, high specific strength, corrosion resistance, and structural design flexibility. However, prolonged exposure to hygrothermal conditions, ultraviolet (UV) radiation, and thermo-oxidative environments can progressively damage these materials, leading to mechanical degradation and shortened service life. This review examines environmental aging in FRP composites at the levels of the polymer matrix, fiber/matrix interface, and reinforcing fibers. Representative predictive models, finite element methods, and experimental characterization techniques are summarized, together with the evolution of mechanical properties under different aging conditions. Hygrothermal degradation is mainly associated with moisture diffusion, matrix swelling, and interfacial debonding, whereas UV and thermo-oxidative aging are largely governed by photo-oxidation and thermally activated free-radical reactions. These processes may induce chain scission, crosslinking, matrix embrittlement, and interface damage. Under coupled environmental exposure, degradation is not simply additive because moisture transport, oxidation kinetics, and failure pathways may interact. Future research should emphasize multiscale characterization, anti-aging modification, interface engineering, protective coatings, and reliability-oriented lifetime prediction. Full article

(This article belongs to the Special Issue Mechanical, Wear, and Functional Properties of Composite Coatings)

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23 pages, 21830 KB

Open AccessArticle

Coupling Interaction of Swirl and Diameter on Particle Deposition and Degradation of Aerodynamic Performance for a Turbine Vane

by Jiajun He, Changce Wang, Li Shi, Rongli Deng, Xiao Tan, Haoyu Zhang, Yue Luo and Jiasheng Song

Coatings 2026, 16(6), 741; https://doi.org/10.3390/coatings16060741 (registering DOI) - 22 Jun 2026

Abstract

This study numerically investigates the effects of inlet swirl intensity on particle deposition on the surface of a static vane by adjusting the inlet swirl intensity and inlet hot streak conditions. The results indicate that swirl significantly alters the vane surface temperature distribution, [...] Read more.

This study numerically investigates the effects of inlet swirl intensity on particle deposition on the surface of a static vane by adjusting the inlet swirl intensity and inlet hot streak conditions. The results indicate that swirl significantly alters the vane surface temperature distribution, increasing the average surface temperature by up to 1.02% under the strongest swirl condition compared to the non-swirl case. On the pressure side, enhanced swirl shifts the high-temperature region toward the vane root, while on the suction side, the overall temperature increases. Particle deposition behavior is strongly size-dependent: swirl reduces the deposition efficiency for small particles but slightly increases it for large particles. Additionally, swirl modifies the deposition pattern, leading to the formation of dart-shaped grooves in the central pressure side and crescent-shaped protrusions near the trailing edge, which in turn affects the aerodynamic performance. The pressure-coefficient fluctuation is predominantly observed on the pressure side. These findings provide insight into the coupled effects of swirl and particle dynamics on vane surface degradation and flow behavior. Full article

(This article belongs to the Special Issue CMAS Penetration, Thermal Insulation Degradation, and Life Prediction of Thermal Barrier Coatings)

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12 pages, 4256 KB

Open AccessArticle

Waterborne Polyurethane-Based Sizing of Carbon Fibers for Improved Interfacial Performance of 3D-Printed Continuous Carbon Fiber/Polylactic Acid Composites

by Weidong Feng, Ling Ding, Wei Ruan, Zhenzhen Quan and Jianyong Yu

Coatings 2026, 16(6), 740; https://doi.org/10.3390/coatings16060740 (registering DOI) - 22 Jun 2026

Abstract

3D-printed continuous carbon fiber-reinforced polylactic acid (CF/PLA) composites combine the high load-bearing capability of continuous fibers with the structural design freedom of additive manufacturing, showing broad application prospects in lightweight complex structures. However, the chemically inert surface of carbon fibers and their insufficient [...] Read more.

3D-printed continuous carbon fiber-reinforced polylactic acid (CF/PLA) composites combine the high load-bearing capability of continuous fibers with the structural design freedom of additive manufacturing, showing broad application prospects in lightweight complex structures. However, the chemically inert surface of carbon fibers and their insufficient interfacial compatibility with the PLA matrix lead to inefficient interfacial load transfer, thereby limiting the mechanical performance of the composites. In this study, a waterborne polyurethane (WPU)-based sizing treatment was applied to carbon fibers to enhance the fiber–matrix interface of 3D-printed continuous CF/PLA composites. The WPU sizing layer increased fiber-bundle cohesion and introduced a transition region between CF and PLA through possible hydrogen bonding, dipolar interactions, and physical adhesion. When the nominal WPU concentration was 5 wt%, the apparent interfacial shear strength reached 1.31 MPa, representing an improvement of approximately 65% compared with ACF/PLA. The three-point flexural strength reached 69.76 MPa, which was 55.3% higher than that of the ACF/PLA composite. These results indicate that WPU sizing is an effective and scalable interfacial regulation strategy for improving the mechanical properties of 3D-printed continuous CF/PLA composites. Full article

(This article belongs to the Special Issue Novel Materials and Coatings for Functional, Protective, and Sustainable Textiles and Wearables)

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19 pages, 28769 KB

Open AccessArticle

Differences in Microstructure and Properties of 16 mm Thick 6082 Aluminum Alloy Under Different Heat Source Conditions

by Zan Ju, Ruxu Huang, Xiaozhong Xie, Shu Liu, Feiyun Wang and Juan Fu

Coatings 2026, 16(6), 739; https://doi.org/10.3390/coatings16060739 (registering DOI) - 21 Jun 2026

Abstract

6082 aluminum alloy is widely applied in marine engineering, rail transportation and other industries owing to its excellent comprehensive performance. Welding heat source characteristics exert a decisive influence on the microstructure and mechanical properties of welded joints and become a major constraint for [...] Read more.

6082 aluminum alloy is widely applied in marine engineering, rail transportation and other industries owing to its excellent comprehensive performance. Welding heat source characteristics exert a decisive influence on the microstructure and mechanical properties of welded joints and become a major constraint for the application of medium-thick aluminum alloy welded structures. In this work, comparative tests of TIG and MIG welding were carried out on 16 mm thick 6082 aluminum alloy plates. Combining thermal simulation, metallographic observation and mechanical property tests, the temperature field distribution, microstructure, microhardness, tensile properties and bending properties of the two kinds of joints were systematically studied. The results show that TIG welding possesses high heat input, forming a broad temperature field with steep thermal gradients. Its weld microstructure is coarse and accompanied by severe coarsening of Mg₂Si precipitates, and the joint presents a highly fluctuating M-shaped microhardness distribution. The average tensile strength of TIG welded joints is 194 MPa, and all specimens fracture in the heat-affected zone. By contrast, MIG welding with low heat input produces a uniform temperature field, as well as a fine and homogeneous weld microstructure with dispersed precipitates. Its microhardness distribution is stable, and the average tensile strength reaches 256 MPa, 32% higher than that of TIG joints. Both welding methods deliver favorable bending performance. The difference in heat input and cooling behavior changes the grain evolution and precipitate characteristics and further dominates the final mechanical performance of joints. MIG welding is more suitable for multi-layer, multi-pass welding of 16 mm thick 6082 aluminum alloy. This work clarifies the correlation between heat input, microstructure and mechanical properties, and the optimized process can effectively improve the microstructural uniformity of the weld joint and enhance its mechanical properties. Full article

(This article belongs to the Special Issue Laser-Based Additive Manufacturing and Surface Engineering for Advanced Coatings)

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13 pages, 773 KB

Open AccessArticle

Material Microstructure and Mechanical Properties of Spark Plasma-Sintered Al_0.2CoCrFeNi-5%WC High-Entropy Alloy Composites: A Sintering Temperature Study

by Hui Liang, Ziwen Hong, Qian Liu, Jingzhuo Zhang, Jinxin Hou, Dongxu Qiao, Yangming Liu, Hanshu Zhao, Yingfan Zhai, Kaiyue Yang, Li Jiang, Jinhu Yu and Zhiqiang Cao

Coatings 2026, 16(6), 738; https://doi.org/10.3390/coatings16060738 (registering DOI) - 21 Jun 2026

Abstract

Al_0.2CoCrFeNi-5%WC high-entropy alloy (HEA) composites were fabricated via spark plasma sintering at temperatures ranging from 900°C to 1050°C, and the effects of sintering temperature on phase constitution, microstructure, and mechanical properties were systematically investigated. The results show that all composites consist [...] Read more.

Al_0.2CoCrFeNi-5%WC high-entropy alloy (HEA) composites were fabricated via spark plasma sintering at temperatures ranging from 900°C to 1050°C, and the effects of sintering temperature on phase constitution, microstructure, and mechanical properties were systematically investigated. The results show that all composites consist predominantly of an FCC matrix, WC, M₂₃C₆ and M₆C carbides. With increasing sintering temperature, interfacial reactions are promoted, leading to the progressive consumption of WC and an increase in carbide content. The composite sintered at 1000 °C achieves the optimal combination of properties, with a relative density of 96.8%, a yield strength of 468 MPa, an ultimate compressive strength of 1871 MPa, and a fracture strain of 43.6%. The outstanding strength–ductility synergy originates from near-full densification, robust interfacial bonding, and multiple carbide strengthening mechanisms. Excessively high sintering temperature (1050 °C) results in reinforcement coarsening and degradation of mechanical properties. Full article

(This article belongs to the Section Composite Coatings)

18 pages, 4371 KB

Open AccessArticle

Preparation of High-Quality Low-Temperature PECVD Silicon Nitride Films: Effect of NH₃ Precursor on Film Properties and RF Response Mechanism

by Zhen Tang, Peng Yu, Yanli Qi, Zhuo Wang, Jianping Ning and Zhaohui Ren

Coatings 2026, 16(6), 737; https://doi.org/10.3390/coatings16060737 (registering DOI) - 21 Jun 2026

Abstract

With the shift in advanced packaging toward 3D integration and flexible electronics, it is becoming critical to produce high-quality silicon nitride films under low thermal budgets. To overcome the limitations of low-temperature deposition, this study compares two gas mixtures—SiH₄/NH₃/N [...] Read more.

With the shift in advanced packaging toward 3D integration and flexible electronics, it is becoming critical to produce high-quality silicon nitride films under low thermal budgets. To overcome the limitations of low-temperature deposition, this study compares two gas mixtures—SiH₄/NH₃/N₂ and SiH₄/N₂—in plasma-enhanced chemical vapor deposition of silicon nitride coatings. We systematically evaluated how the NH₃ precursor affects deposition kinetics, chemical bonds, non-uniformity, optical properties, and internal stress at different RF powers and electrode gaps. The test results show that NH₃, with its lower dissociation energy, avoids the high activation barrier associated with pure N₂ plasma, leading to a higher reactive nitrogen flux and a doubled deposition rate. In the SiH₄/NH₃/N₂ system, raising RF power from 300 W to 900 W reduced hydrogen content from 23.58% to 12.25%. This suppression of hydrogen promoted structural densification, shifting the mechanical stress from 173.3 MPa to −989.7 MPa. At a larger electrode gap of 19 mm, NH₃’s better diffusion characteristics offset the electric field sensitivity typical of N₂ systems, reducing large-area film non-uniformity by 28.7% compared to a 13 mm gap. This work offers a practical, mass-production-friendly approach for depositing robust, low-hydrogen, highly uniform silicon nitride films at low temperatures. Full article

(This article belongs to the Special Issue 2D Materials-Based Thin Films and Coatings, 2nd Edition)

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55 pages, 2334 KB

Open AccessReview

Electrospun Nanofibers for Antimicrobial Therapy: From Polymer Design to Controlled Drug Release

by Andrei Teodor Matei, Oana Cramariuc, Irina Negut and Iuliana Gabriela Lupu

Coatings 2026, 16(6), 736; https://doi.org/10.3390/coatings16060736 (registering DOI) - 20 Jun 2026

Abstract

The rapid emergence of antimicrobial resistance has intensified the need for advanced therapeutic platforms capable of improving the efficacy, stability, and targeted delivery of antimicrobial agents. Electrospun nanofibers have emerged as highly promising materials for biomedical applications due to their large surface area, [...] Read more.

The rapid emergence of antimicrobial resistance has intensified the need for advanced therapeutic platforms capable of improving the efficacy, stability, and targeted delivery of antimicrobial agents. Electrospun nanofibers have emerged as highly promising materials for biomedical applications due to their large surface area, high porosity, tunable morphology, and ability to incorporate a broad range of bioactive compounds. This review provides a comprehensive overview of the design, fabrication, and biomedical applications of electrospun bioactive nanofibers functionalized with antimicrobial drugs. It presents the main nanofiber fabrication techniques, with particular emphasis on electrospinning and the influence of solution, process, and environmental parameters on fiber morphology and drug-loading efficiency. Natural, synthetic, and hybrid polymer systems commonly employed in electrospun antimicrobial nanofibers are analyzed in relation to their physicochemical properties, biocompatibility, and therapeutic performance. In addition, the review highlights different drug incorporation strategies, including encapsulation, immobilization, and surface coating, as well as the mechanisms of action of antimicrobial agents. Recent advances in nanotechnology-based antimicrobial systems and their role in overcoming analytical, biopharmaceutical, and drug-delivery limitations are also examined. Furthermore, the review addresses current challenges related to scalability, reproducibility, stability, and clinical translation of electrospun nanofibers. Finally, future perspectives focusing on multifunctional, stimuli-responsive, and personalized antimicrobial nanofiber systems are discussed as promising directions for combating bacterial infections and reducing the global burden of antimicrobial resistance. Full article

(This article belongs to the Special Issue Advanced Surface Modifications for Biomedical Applications: Enhancing Biocompatibility and Bioactivity)

15 pages, 26045 KB

Open AccessArticle

Crystal Plasticity Finite Element Simulation and Quasi-In-Situ Experimental Study of Tensile Strain Partitioning in Multiphase High-Strength Steel

by Qilong Jia, Bingyi Wang, Yafei Xue, Lin Zhang, Yi Sun, Sujuan Yuan, Dongyun Sun, Peng Zhang, Xiaowen Sun, Xiaoyong Feng and Fucheng Zhang

Coatings 2026, 16(6), 735; https://doi.org/10.3390/coatings16060735 (registering DOI) - 20 Jun 2026

Abstract

A multiphase high-strength steel austempered at 260 °C for 24 h was investigated by quasi-in-situ tensile characterization and EBSD-based crystal plasticity finite element modeling. The experimental observations reveal that local plastic deformation is strongly heterogeneous: von Mises strain concentrates preferentially near bainitic-ferrite packets, [...] Read more.

A multiphase high-strength steel austempered at 260 °C for 24 h was investigated by quasi-in-situ tensile characterization and EBSD-based crystal plasticity finite element modeling. The experimental observations reveal that local plastic deformation is strongly heterogeneous: von Mises strain concentrates preferentially near bainitic-ferrite packets, phase boundaries, and retained-austenite/martensite–austenite regions, whereas blocky retained austenite contributes to strain accommodation at the early deformation stage. To quantify the underlying stress–strain partitioning, a quasi-two-dimensional representative volume element was reconstructed from EBSD data and implemented in ABAQUS through a user-defined material subroutine. The model contained the real grain morphology, phase distribution, and crystal orientation information of the 24 h austempered specimen. A rate-dependent crystal plasticity constitutive framework with BCC matrix, FCC retained austenite, and transformed martensite branches was calibrated against the macroscopic tensile curve. The simulated tensile response agrees well with the experimental curve before macroscopic instability, and the predicted local fields are consistent with the quasi-in-situ strain maps. The results show that local plastic strain first accumulates in M/A-related regions and phase-boundary-neighboring zones, while high Mises stress migrates dynamically with slip activity and stress-induced martensitic transformation. Retained-austenite transformation increases the local load-bearing capacity, modifies interphase load transfer, and delays the direct linkage of strain-localization bands. The present work clarifies the coupling among retained-austenite stability, TRIP-assisted load redistribution, and microstructural strain partitioning in multiphase high-strength steel, providing a mesoscale basis for microstructure-guided strength–ductility optimization. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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16 pages, 32529 KB

Open AccessArticle

Quantitative Analysis of the Effect of Rolling Process on the Mechanical Properties of Mg-Sm Alloy

by Jianchao Chen, Bo Guan, Wenzheng Liu, Jiahao Wang, Jing Xu, Hong Yan, Qiang Hu and Yunchang Xin

Coatings 2026, 16(6), 734; https://doi.org/10.3390/coatings16060734 (registering DOI) - 19 Jun 2026

Abstract

Magnesium (Mg) alloy sheets usually suffer from severe mechanical anisotropy and a trade-off between strength and ductility. In this work, the effects of rolling temperature (200 °C and 400 °C) and rolling speed (50–1000 r/min) on the microstructure and mechanical properties of a [...] Read more.

Magnesium (Mg) alloy sheets usually suffer from severe mechanical anisotropy and a trade-off between strength and ductility. In this work, the effects of rolling temperature (200 °C and 400 °C) and rolling speed (50–1000 r/min) on the microstructure and mechanical properties of a Mg-1Sm (samarium, Sm) (wt.%) alloy were systematically investigated. Low-temperature rolling (200 °C) results in high dislocation density and a double-peak basal texture in Mg-1Sm alloy, causing very limited plasticity and a pronounced anisotropy with a lower yield strength along the rolling direction (RD) than along the transverse direction (TD). A significantly improved mechanical property (yield strength of ~196 MPa, elongation of 18.4% and near-isotropy) can be achieved in the Mg-1Sm alloy by optimizing the rolling conditions (400 °C, 500 r/min). The findings indicate that increasing the temperature is beneficial for activating non-basal slip and multiple twinning modes, thereby weakening and dispersing the basal texture, which can efficiently improve the anisotropic properties. Increasing the rolling speed can promote the recrystallization process, resulting in the enhancement of plasticity. Quantitative analyses reveal that the reduction in dislocation density and the suppression of Sm segregation at grain boundaries under high-temperature high-speed rolling are responsible for the improved ductility and reduced anisotropy. Full article

(This article belongs to the Section Metal Surface Process)

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16 pages, 38069 KB

Open AccessArticle

Fabrication, Microstructural and Micro-Mechanical Characterization of Ti-Nb-HA Composite Under Micro-Pillar Compression

by Abdulaziz Kurdi, Doaa Almalki, Husain Alnaser, Ahmed Degnah and Animesh Kumar Basak

Coatings 2026, 16(6), 733; https://doi.org/10.3390/coatings16060733 (registering DOI) - 19 Jun 2026

Abstract

The present work reports on the microstructural and micro-mechanical characterization of Ti-Nb-HA-based composites. The composites were prepared via a spark plasma sintering (SPS) consolidation process. The effect of two distinct levels of hydroxyapatite (HA) content (e.g., 10 and 20 wt.%) on the microstructural [...] Read more.

The present work reports on the microstructural and micro-mechanical characterization of Ti-Nb-HA-based composites. The composites were prepared via a spark plasma sintering (SPS) consolidation process. The effect of two distinct levels of hydroxyapatite (HA) content (e.g., 10 and 20 wt.%) on the microstructural and micro-mechanical properties were investigated via in situ micro-pillar compression, and the results were compared against a sole Ti-Nb composite. The microstructure of the composites was composed of parent Ti and Nb grains, together with the reaction products; due to the decomposition of HA, there was a rise in different biocompatible phases. The Vickers hardness of the composite was sensitive to applied loads due to the presence of pores and voids, which was foreseen to be beneficial when the composite was used as an implant, according to the literature. The addition of 20 wt.% HA causes a decrease in hardness to 990 HV, compared to 1109 HV for 10 wt.% HA and 1275 HV for sole Ti-Nb. The addition of HA into Ti-Nb also lowers the compressive strength from 553 MPa for Ti-Nb to 189 MPa for Ti-30Nb-20HA. This was accompanied by a reduction in the elastic modulus, from 130 GPa for Ti-Nb to 29 GPa for Ti-30Nb-20HA. The deformation mechanism was ductile-dominated in all cases, with the presence of a quasi-brittle nature for HA-containing composites. Full article

(This article belongs to the Section Metal Surface Process)

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19 pages, 5438 KB

Open AccessArticle

Influence of Titanium Concentration on Piezoresistive Characteristics of DLC:Ti Films

by Weihao Lun, Shihao Shi, Zhengtao Wu, Haiqing Li, Qimin Wang and Yisong Lin

Coatings 2026, 16(6), 732; https://doi.org/10.3390/coatings16060732 (registering DOI) - 19 Jun 2026

Abstract

Titanium-doped diamond-like carbon (DLC:Ti) films were deposited by magnetron sputtering. The effects of Ti concentration on the microstructure, phase composition and piezoresistive properties of the films were systematically investigated. The surface morphology, crystal structure and chemical bonding states of the samples were characterized [...] Read more.

Titanium-doped diamond-like carbon (DLC:Ti) films were deposited by magnetron sputtering. The effects of Ti concentration on the microstructure, phase composition and piezoresistive properties of the films were systematically investigated. The surface morphology, crystal structure and chemical bonding states of the samples were characterized using SEM, XRD and XPS. The piezoresistive properties were then assessed by monitoring the resistance change in the thin films using a precision resistance meter under controlled external stimulation. The results demonstrate that the sp²/sp³ ratio of the DLC:Ti films increases with rising Ti concentration, and both Ti–C and Ti–Ti chemical bonds are formed within the films. An excessive β-Ti phase forms when the Ti concentration exceeds 39.7 at.%. The electrical resistance of DLC:Ti films decreases linearly as the applied normal stress increases from 0 to 35 MPa, with a maximum piezoresistive coefficient of −9.0 × 10⁻² GPa⁻¹ achieved for the film with a Ti doping concentration of 12.9 at.%. One hundred cyclic loading–unloading tests induce the structural transition from sp³ to sp², resulting in the graphitization of DLC:Ti films. In addition, external stress facilitates the fracture of Ti–C bonds and the relaxation of residual stress in the DLC:Ti films; the β- to α-Ti phase transformation induced by external loading is also observed in the films. Cyclic piezoresistive tests reveal that the piezoresistive stability of the DLC:Ti films is enhanced with increasing Ti concentration, which is attributed to the increased formation of Ti–C bonds in the films. Full article

(This article belongs to the Topic Advances in Coatings Technology and Their Multidisciplinary Applications)

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14 pages, 6695 KB

Open AccessArticle

Anisotropic Mechanical Behavior and Localized Deformation Evolution in Q420 High-Strength Steel

by Nan Guo, Yangyang Li, Yaoyao Li, Xiqiang Ma, Xiao Wang and Chunyang Liu

Coatings 2026, 16(6), 731; https://doi.org/10.3390/coatings16060731 (registering DOI) - 18 Jun 2026

Abstract

Q420 high-strength steel exhibits pronounced anisotropy due to its rolling process, and conventional uniaxial tensile testing is incapable of acquiring strain field evolution information during the local necking stage. In this study, quasi-static uniaxial tensile tests were conducted on Q420 cold-rolled high-strength steel [...] Read more.

Q420 high-strength steel exhibits pronounced anisotropy due to its rolling process, and conventional uniaxial tensile testing is incapable of acquiring strain field evolution information during the local necking stage. In this study, quasi-static uniaxial tensile tests were conducted on Q420 cold-rolled high-strength steel sheets at six orientations (0°, 15°, 30°, 45°, 60°, and 90°) using Digital Image Correlation (DIC) technology. The evolution of the strain field and the corresponding stress–strain responses at different orientations were systematically investigated. The results show that the DIC technique effectively captured the full-field strain evolution of the specimens from uniform deformation to local necking and final fracture in all directions. Taking the 0° direction as an example, the local maximum engineering strain prior to fracture reached 35.866%, whereas the average fracture strain within the gauge section was only approximately 22.5%, corresponding to a ratio of approximately 1.6 and clearly demonstrating the severe strain concentration within the necking zone. The stress–strain curves corresponding to different rolling directions exhibited pronounced anisotropy. The tensile strength was highest in the 90° direction and lowest in the 0° direction; however, the 0° direction exhibited the best ductility, whereas the 45° direction showed the poorest ductility. Among the six orientations, the midpoint transverse engineering strain exhibited the largest absolute value in the 45° direction, further indicating that this orientation is the most susceptible to plastic instability. In this work, DIC-based full-field measurement was combined with multi-directional tensile testing to quantitatively characterize the relationship between local strain concentration and anisotropy. The findings provide high-precision experimental data for the calibration of anisotropic constitutive models and the optimization of forming processes. Full article

(This article belongs to the Special Issue Laser Welding and Cladding for Enhanced Mechanical Performance)

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25 pages, 13672 KB

Open AccessArticle

Seismic Fragility Assessment of Reinforced Concrete Bridge Under Near-Fault Pulse-like Ground Motions Considering Structural Parameter Uncertainties

by Zekai Ma, Chao Yin, Jiagu Chen and Jiaxu Li

Coatings 2026, 16(6), 730; https://doi.org/10.3390/coatings16060730 (registering DOI) - 18 Jun 2026

Abstract

Near-fault pulse-like ground motions (NFPLGMs) impose concentrated energy demands that can severely damage bridges, yet their scarcity and the influence of structural parameter uncertainties are often neglected in seismic fragility assessments. This study proposed a synthesis method for NFPLGMs by superposing low-frequency pulse [...] Read more.

Near-fault pulse-like ground motions (NFPLGMs) impose concentrated energy demands that can severely damage bridges, yet their scarcity and the influence of structural parameter uncertainties are often neglected in seismic fragility assessments. This study proposed a synthesis method for NFPLGMs by superposing low-frequency pulse components (extracted via the Gabor wavelet transform and low-pass filtering) with high-frequency stochastic components based on an evolutionary power spectrum. A three-span reinforced concrete bridge was modeled in OpenSeesPy, and Incremental Dynamic Analysis (IDA), together with a quadratic response surface model, were used to plot seismic fragility curves. The damping ratio (ξ), elastic modulus of steel reinforcement (E_s), yield strength of steel reinforcement (f_y), diameter of longitudinal reinforcement (D), and peak ground acceleration (PGA) were treated as random variables. Sensitivity indices were computed using Monte Carlo sampling (n = 10,000). Results show that ξ most strongly affects the displacement ductility ratio of the bridge pier (u_d) (variation of up to 32.6%), while E_s dominates the shear deformation of the bridge bearing (d) (variation of up to 43.8%). Neglecting structural parameter uncertainties overestimates median PGA thresholds (m_R) for different damage states by 1.5%–36.1%, and replacing NFPLGMs with ordinary ground motions overestimates seismic capacity by 1.7%–36.6%. The bridge bearing is consistently more vulnerable than the pier, with a collapse probability of 0.9566 at PGA = 1.0 g. These findings highlight the necessity of incorporating both NFPLGM characteristics and structural parameter uncertainties into bridge seismic fragility assessment. On the other hand, when seismic retrofitting of bridges is carried out using coating materials, priority should be given to more vulnerable components, such as bridge bearings, to improve the utilization efficiency of limited resources. Full article

(This article belongs to the Special Issue Surface Treatments and Coatings for Asphalt and Concrete)

12 pages, 12569 KB

Open AccessArticle

Microstructural Evolution and Thermal Transport in APS SrZrO₃ Coatings: An EBSD-Focused Study

by Matiullah Khan and Yi Zeng

Coatings 2026, 16(6), 729; https://doi.org/10.3390/coatings16060729 (registering DOI) - 18 Jun 2026

Abstract

This work reports the combination of pentagonal grain morphology, high phase purity, and non-monotonic thermal conductivity behavior over a wide temperature range (25–1200 °C). The SrZrO₃ coatings with different processing parameters are deposited using atmospheric plasma spraying (APS). Unlike conventional atmospheric plasma-sprayed [...] Read more.

This work reports the combination of pentagonal grain morphology, high phase purity, and non-monotonic thermal conductivity behavior over a wide temperature range (25–1200 °C). The SrZrO₃ coatings with different processing parameters are deposited using atmospheric plasma spraying (APS). Unlike conventional atmospheric plasma-sprayed oxide coatings, distinct pentagonal-shaped grains with multi-directional orientation suggest a unique solidification pathway and anisotropic growth mechanism. The pentagonal morphology may come from the impingement of five radially columnar grain sectors during rapid solidification of a highly undercooled melt splat, constrained by local thermal gradients. This atypical morphology, not commonly reported for SrZrO₃ coatings, is further supported by electron backscatter diffraction (EBSD) results, which confirm a remarkably high phase fraction (~94.5%) of SrZrO₃ despite rapid quenching inherent to APS processing. The combination of high phase purity and unusual grain geometry represents a significant advancement in tailoring the microstructures of environmental barrier materials. Moreover, the non-linear thermal conductivity response with temperature shows a pronounced decrease up to ~800 °C (0.737 W·m⁻¹·K⁻¹) stabilization between 800 and 900 °C, and a subsequent increase at higher temperatures. This behavior indicates a complex interplay between phonon scattering, defect structures, and possible radiative heat transfer contributions at elevated temperatures. Full article

(This article belongs to the Special Issue Performance and Applications of Environmental Barrier Coatings (EBCs)/Thermal Barrier Coatings (TBCs))

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19 pages, 11931 KB

Open AccessArticle

Crack Suppression and Performance Analysis of Novel Ni60 Alloy Hardbanding on Drillpipes via Laser Cladding

by Lilan Liu, Shen Wang, Yingkai Qin, Boyu Guo, Ziying Wu and Feiyan Han

Coatings 2026, 16(6), 728; https://doi.org/10.3390/coatings16060728 (registering DOI) - 18 Jun 2026

Abstract

With the continuous advancement of drilling technologies for deep and ultra-deep well operations, drillpipes are subjected to increasingly severe wear and corrosion conditions. To enhance the wear and corrosion resistance of drillpipe surfaces, this study developed a novel Ni60 alloy hardbanding via laser [...] Read more.

With the continuous advancement of drilling technologies for deep and ultra-deep well operations, drillpipes are subjected to increasingly severe wear and corrosion conditions. To enhance the wear and corrosion resistance of drillpipe surfaces, this study developed a novel Ni60 alloy hardbanding via laser cladding technology. To solve the problem of crack sensitivity, the cracking mechanism of Ni60 coatings directly deposited on 4137H steel substrates was systematically investigated and a crack suppression strategy was proposed. By employing a 316L translation layer between the 4137H substrate and the Ni60 alloy coating, the interfacial thermal stress induced by the mismatch of thermal expansion coefficients between dissimilar materials was relieved. Therefore, crack-free 316L-Ni60 gradient coatings were obtained. The microstructure, phase composition, and mechanical properties of the coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and microhardness testing. The experimental results demonstrate that the 316L-Ni60 gradient coating exhibits a homogeneous microstructure and forms a dense metallurgical bond with the 4137H steel. The microhardness of the coating is 2.2 times that of the 4137H steel, while its wear rate is reduced by nearly half. Furthermore, the Ni60 coating possesses higher corrosion resistance compared with 4137H steel. This study promotes the potential application of the Ni60 alloy coating as a new type of hardbanding on drillpipes. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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17 pages, 3501 KB

Open AccessArticle

Microstructure and Mechanical Properties of YSZ Coating in TBCs on Rotating Curved Substrates Deposited at Different Standoff Distances

by Pan Li, Hui Dong, Yukun Feng, Yong Zhou and Lishuang Wang

Coatings 2026, 16(6), 727; https://doi.org/10.3390/coatings16060727 (registering DOI) - 18 Jun 2026

Abstract

To address the issue of depositing thermal barrier coatings (TBCs) on rotating curved surfaces, atmospheric plasma spraying (APS) was employed to prepare yttria partially stabilized zirconia (YSZ) coatings on a rotating curved substrate. Three standoff distances of 80 mm, 100 mm and 120 [...] Read more.

To address the issue of depositing thermal barrier coatings (TBCs) on rotating curved surfaces, atmospheric plasma spraying (APS) was employed to prepare yttria partially stabilized zirconia (YSZ) coatings on a rotating curved substrate. Three standoff distances of 80 mm, 100 mm and 120 mm were selected. The microstructure, microhardness, elastic modulus and fracture toughness of three YSZ coatings were tested. The results indicate that as the standoff distance increased from 80 mm to 120 mm, porosity increased from 11.27% to 13.29%, microhardness decreased from 760.8 HV_0.3 to 713.2 HV_0.3, elastic modulus decreased from 24.0 GPa to 22.6 GPa, and fracture toughness decreased from 1.14 MPa·m^1/2 to 1.04 MPa·m^1/2. The properties of the YSZ coating in the case, such as elastic modulus and fracture toughness, were significantly lower than those of the YSZ coating deposited on stationary planar substrates. Solidification of the molten particles impacted on rotating curved substrates was accelerated and splat spreading was constrained because of the coupled effect of centrifugal force and elevated cooling rate. Therefore, under identical spraying parameters, the process parameters optimized for planar substrates cannot be directly transferred to rotating curved components. Full article

(This article belongs to the Special Issue Novel Protective Coatings on Anti-Oxidation, Anti-Wear, and Corrosion Resistance Properties)

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17 pages, 3223 KB

Open AccessArticle

The Mechanical Strengths and Resistance to Chloride Salt Erosion of Iron Tailings Powder with Self-Compacting Concrete with Hybrid Fibers

by Ligai Bai, Chenxi Gao, Guihua Yang, Youheng Zhang, Huamin Cai, Feiting Shi and Wenxiu Guo

Coatings 2026, 16(6), 726; https://doi.org/10.3390/coatings16060726 - 18 Jun 2026

Abstract

In this study, the fluidity and the flexural and compressive strengths of self-compacting concrete with iron tailings powder are measured. The influence of basalt fibers and steel fibers on the mechanical strengths and the attenuation of performance after NaCl erosion has been investigated. [...] Read more.

In this study, the fluidity and the flexural and compressive strengths of self-compacting concrete with iron tailings powder are measured. The influence of basalt fibers and steel fibers on the mechanical strengths and the attenuation of performance after NaCl erosion has been investigated. The mass ratio of iron tailings powder ranges from 0% to 20%. The volume ratio of fibers increases from 0% to 3.5%. The influence of hybrid basalt-steel fibers is considered. The results indicate that the mechanical properties vary in the form of cubic functions with the mass ratio of iron tailings powder and the volume ratio of fibers. Specimens with 15% iron tailings powder exhibit the highest mechanical performance. At this dosage, the flexural and compressive strengths are increased by rates of 12.2% and 8.5%, respectively. Specimens reinforced with 2% basalt fibers or 2.5% steel fibers individually exhibit the highest mechanical performance, the lowest chloride ion impermeability, and the best resistance to chloride salt erosion. The hybrid combination of 0.5% basalt fibers and 3% steel fibers provides the optimal fiber dosage. An amount of 2% basalt fibers or 2% steel fibers increase the flexural strengths by rates of up to 48.9% and 84.8%, respectively, while the corresponding compressive strengths are increased by up to 12.5% and 20.9%. The chloride ion migration coefficient of specimens are decreased by up to 37.86%, 30%, and 42.14% with 2.5% basalt fibers, 2% steel fibers, and a hybrid combination of 1.5% basalt fibers and 1% steel fibers, respectively. Specimens with 15% iron tailings powder exhibit the highest amount of dense hydration products and the least amount of cracks. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials, 2nd Edition)

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