Coatings

15 pages, 28154 KiB

Open AccessArticle

Study on the Cutting Performance and Remaining Life Prediction of Micro-Texture Ball End Milling Cutters for Titanium Alloys

by Yuhua Zhang, Yongqi Fu, Quanxi Li, Keyi Zhang and Kuo Liu

Coatings 2024, 14(7), 814; https://doi.org/10.3390/coatings14070814 (registering DOI) - 29 Jun 2024

Abstract

As a fundamental machining tool, the ball end milling cutter plays a crucial role in manufacturing. Due to its low thermal conductivity, the heat generated during the cutting process of titanium alloy materials is not dissipated efficiently, resulting in a substantial cutting heat. [...] Read more.

As a fundamental machining tool, the ball end milling cutter plays a crucial role in manufacturing. Due to its low thermal conductivity, the heat generated during the cutting process of titanium alloy materials is not dissipated efficiently, resulting in a substantial cutting heat. This heat leads to chip adhesion and exacerbates the wear of the ball end milling cutter, ultimately affecting its service life. Therefore, studying the residual life of the tool during the cutting process is essential to prevent significant impacts on the product’s surface quality due to tool damage and passivation. Most research on micro-texture cutters is based on experiments that analyze the wear patterns of cutters under various lubrication conditions and their influence on the cutting process. Different neural network prediction models are employed to enhance the accuracy and stability of tool life prediction models. However, the exploration of other superior models for predicting the life of micro-texture cutters remains ongoing. This paper is based on an experiment involving the milling of titanium alloy using a micro-pit-structured ball end milling cutter. It was found that the cutting force of the tool is higher during the initial and later wear stages. During the stable wear stage, the unevenness of the defective layer on the tool surface is reduced, increasing the contact area and reducing the surface pressure, thereby decreasing the cutting force. This study analyzes the influence of micro-pit structural parameters on the wear and milling force of the ball end milling cutter. By evaluating the wear value of the ball end milling cutter after each cut, the wear mechanism of the micro-texture cutter is identified. A deep-learning-based bidirectional long short-term memory (BiLSTM) neural network model for tool life prediction is developed. Through training and validation, the model’s accuracy and stability are continuously improved. A comparative analysis with different predictive models is conducted to determine whether the proposed model offers advantages over existing models, which is crucial for maximizing tool utilization and reducing manufacturing costs. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

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15 pages, 9221 KiB

Open AccessArticle

Tribological Properties of Laser-Cladded NiCrBSi Coatings Undergoing Friction with Ti6Al4V Alloys

by Mingzhen Fan, Pengcheng Du, Ke Wen, Ruizhi Zhang, Siliang Yu and Tongzhou Chen

Coatings 2024, 14(7), 813; https://doi.org/10.3390/coatings14070813 (registering DOI) - 28 Jun 2024

Abstract

This work aims at reducing abrasion between titanium alloy parts, such as drive shafts and support pairs used in aviation. Three different NiCrBSi coatings, Ni40, Ni50, and Ni60, are prepared on surfaces of Ti6Al4V by laser cladding. The microstructural and mechanical properties of [...] Read more.

This work aims at reducing abrasion between titanium alloy parts, such as drive shafts and support pairs used in aviation. Three different NiCrBSi coatings, Ni40, Ni50, and Ni60, are prepared on surfaces of Ti6Al4V by laser cladding. The microstructural and mechanical properties of these coatings are analyzed by scanning electron microscope (SEM) and a microhardness tester. The tribological properties of the NiCrBSi coatings undergoing friction with Ti6Al4V are tested using a wear testing machine. The results show that the Vickers hardnesses of the Ni40, Ni50, and Ni60 coatings are 490 HV₀.₃, 609 HV₀.₃, and 708 HV₀.₃, respectively. For the above NiCrBSi coatings, more hard phases are produced with increases in the amounts of Cr in the powders, resulting in increases in the coatings’ hardnesses. The wear test results show that the NiCrBSi coatings could reduce the friction coefficients, which gradually decreased with increases in the coatings’ hardnesses. Both the coating-specific wear rates and the friction pair wear losses initially decreased and then increased. The Ni50 coating and the Ti6Al4V friction pair undergoing friction with the Ni50 coating showed the best wear performance, with a specific wear rate and wear loss of 0.51 × 10⁻⁷ mm³/(N·m) and 7.8 mg, respectively. The specific wear rates for Ni50 were only 8.4%, 35.4%, and 37.0% of the Ti6Al4V, Ni40, and Ni60, respectively. In addition, the friction pair wear loss was only 36.4%, 52.5%, and 55.3% of that while undergoing friction with Ti6Al4V, Ni40, and Ni60, respectively. The NiCrBSi coatings prepared on the surface of Ti6Al4V show excellent antifriction and wear resistance properties, providing a viable solution for the design of wear-resistant coatings on load-bearing and non-load-bearing titanium alloy parts. Full article

(This article belongs to the Section Tribology)

24 pages, 3343 KiB

Open AccessArticle

Design of Tool Wear Monitoring System in Bone Material Drilling Process

by Lijia Liu, Wenjie Kang, Yiwen Wang and Lingchen Zeng

Coatings 2024, 14(7), 812; https://doi.org/10.3390/coatings14070812 (registering DOI) - 28 Jun 2024

Abstract

Biological bone materials, complex and anisotropic, require precise machining in surgeries. Bone drilling, a key technique, is susceptible to increased friction from tool wear, leading to excessive forces and high temperatures that can damage bone and surrounding tissues, affecting recovery. This study develops [...] Read more.

Biological bone materials, complex and anisotropic, require precise machining in surgeries. Bone drilling, a key technique, is susceptible to increased friction from tool wear, leading to excessive forces and high temperatures that can damage bone and surrounding tissues, affecting recovery. This study develops a monitoring platform to assess tool wear during bone drilling, employing an experimental setup that gathers triaxial force and vibration data. A recognition model using a bidirectional long short-term memory network (BI-LSTM) with a multi-head attention mechanism identified wear levels. This model, termed ABI-LSTM, was optimized and benchmarked against SVR, RNN, and CNN models. The results from implementing the ABI-LSTM-based monitoring system demonstrated its efficacy in detecting tool wear, thereby potentially reducing surgical risks such as osteonecrosis and drill breakage, and enhancing surgical outcomes. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

25 pages, 2737 KiB

Open AccessArticle

A Comparative Study on Al_0.6Ti_0.4N Coatings Deposited by Cathodic Arc and HiPIMS in End Milling of Stainless Steel 316L

by Victor Saciotto, Qianxi He, Monica C. Guimaraes, Jose M. DePaiva, Joern Kohlscheen, Luis C. Fontana and Stephen C. Veldhuis

Coatings 2024, 14(7), 811; https://doi.org/10.3390/coatings14070811 (registering DOI) - 28 Jun 2024

Abstract

The machining of austenitic stainless steel alloys is usually characterized by high levels of adhesion and built-up edge; therefore, improving tribological conditions is fundamental to obtaining higher tool life and better surface finish. In this work, three different Al_0.6Ti_0.4N [...] Read more.

The machining of austenitic stainless steel alloys is usually characterized by high levels of adhesion and built-up edge; therefore, improving tribological conditions is fundamental to obtaining higher tool life and better surface finish. In this work, three different Al_0.6Ti_0.4N coatings are compared, two deposited by Cathodic Arc Evaporation (CAE) and one with High-Power Impulse Magnetron Sputtering (HiPIMS). The effects of the micromechanical properties and the microstructure of the coatings were then studied and related to the machining performance. Both arc-deposited coatings (CAE 1 and 2) exhibited similar average tool life, 127 min and 128 min, respectively. Whereas the HiPIMS lasted for only 21.2 min, the HiPIMS-coated tool had a much shorter tool life (more than six times lower than both CAE coatings) due to the intense adhesion that occurred in the early stages of the tool life. This higher adhesion ultimately caused built-up edge and chipping of the tool. This was confirmed by the cutting forces and more deformation on the shear band and undersurface of the chips, which are related to higher levels of friction. The higher adhesion could be attributed to the columnar structure of the HiPIMS and the (111) main texture, which presents a higher surface energy when compared to the dominant (200) from both arc depositions. Studies focused on tribology are necessary to further understand this relationship. In terms of micromechanical properties, tools with the highest plasticity index performed better (CAE 2 = 0.544, CAE 1 = 0.532, and HiPIMS = 0.459). For interrupted cutting machining where adhesion is the main wear mechanism, a reserve of plasticity is beneficial to dissipate the energy generated during friction, even if this was related to lower hardness levels (CAE 2 = 26.6 GPa, CAE 1 = 29.9 GPa, and HiPIMS = 33.6 GPa), as the main wear mechanism was adhesive and not abrasive. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

16 pages, 1088 KiB

Open AccessArticle

Mechanical Performance/Cost Ratio Analysis of Carbon/Glass Interlayer and Intralayer Hybrid Composites

by Weili Wu

Coatings 2024, 14(7), 810; https://doi.org/10.3390/coatings14070810 (registering DOI) - 28 Jun 2024

Viewed by 65

Abstract

Hybrid composites combining carbon and glass fibers are increasingly studied for their potential to enhance mechanical properties and cost efficiency. Understanding how different hybrid structures influence these properties is critical for optimizing material design and application. In this paper, the mechanical properties of [...] Read more.

Hybrid composites combining carbon and glass fibers are increasingly studied for their potential to enhance mechanical properties and cost efficiency. Understanding how different hybrid structures influence these properties is critical for optimizing material design and application. In this paper, the mechanical properties of carbon/glass (C/G) interlayer and intralayer hybrid composites, including tensile, compressive, and flexural properties, were tested, and the cost performances of hybrid composites were analyzed to assess the economic feasibility of different stacking configurations. It was revealed that the specific tensile, compressive, and flexural modulus/cost and strength/cost ratios of interlayer and intralayer hybrid composites decreased with increasing carbon fiber content, indicating that adding carbon fiber reduced cost performance. With the combined hybrid ratio and the interlayer structure with glass fiber sandwiching carbon fiber, the tensile and compressive properties were the most cost-effective. When the dispersion degree of the intralayer hybrid structure was 0, the tensile and compressive properties were the most cost-effective. Specifically, for intralayer hybrid composites with a dispersion degree of 0 and C:G = 1:4, the specific tensile strength/cost ratio was 6.7 × 10⁴ N·m/USD, and the specific compressive modulus and strength/cost ratio was 3.8 × 10⁶ N·m/USD and 4.7 × 10³ N·m/USD, respectively. However, the flexural performance/cost ratio was found to be opposite to the tensile and compressive results. When carbon fiber was distributed in the bottom layer or used to sandwich the glass fiber, the flexural performance/cost ratio of interlayer hybrid composites was nearly as good as that of glass fiber. Moreover, by considering the working condition of composites, the cost performance of mechanical properties can be optimized and improved through careful design of hybrid ratios and stacking structures. Full article

(This article belongs to the Special Issue Novel Advances in Multi-Layer Fibre-Reinforced Composites)

25 pages, 1601 KiB

Open AccessReview

Corrosion of Anodized Titanium Alloys

by Jesús Manuel Jáquez-Muñoz, Citlalli Gaona-Tiburcio, Ce Tochtli Mendez-Ramirez, Martha Guadalupe Carrera-Ramirez, Miguel Angel Baltazar-Zamora, Griselda Santiago-Hurtado, Maria Lara-Banda, Francisco Estupiñan-Lopez, Demetrio Nieves-Mendoza and Facundo Almeraya-Calderon

Coatings 2024, 14(7), 809; https://doi.org/10.3390/coatings14070809 (registering DOI) - 28 Jun 2024

Viewed by 85

Abstract

Ti and Ti alloys are employed in demanding industries such as aerospace, automotive, biomedical, aeronautic, structural, naval, and chemical, thanks to their resistance to corrosion due to the formation of the TiO₂ film on the surface. Diverse research has established that different [...] Read more.

Ti and Ti alloys are employed in demanding industries such as aerospace, automotive, biomedical, aeronautic, structural, naval, and chemical, thanks to their resistance to corrosion due to the formation of the TiO₂ film on the surface. Diverse research has established that different corrosive media could attack the oxide layer. One way to generate a stable, compact, and continuous oxide film is through anodizing treatment. The efficiency of anodization depends on diverse factors such as the microstructure, chemical composition of alloys, pH of electrolyte, time, and temperature of anodizing. This review aims to examine the corrosion resistance of the anodized layer on Ti and Ti alloys, with different parameters. The discussion is centered on the influence of the different parameters and alloy properties in the effectivity of anodizing when they are characterized by electrochemical techniques while studying the behavior of oxide. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

15 pages, 10572 KiB

Open AccessArticle

Rate-Dependent Evolution of Microstructure and Stress in Silicon Films Deposited by Electron Beam Evaporation

by Runar Plünnecke Dahl-Hansen, Marit Stange, Tor Olav Sunde and Alexander Ulyashin

Coatings 2024, 14(7), 808; https://doi.org/10.3390/coatings14070808 - 28 Jun 2024

Viewed by 129

Abstract

Growing high-quality Si films at high rates with thicknesses ranging from the few nm- to µm-range while keeping the material consumption at a minimum is important for a wide range of Si-based technologies, spanning from batteries to sensors and solar cells. In this [...] Read more.

Growing high-quality Si films at high rates with thicknesses ranging from the few nm- to µm-range while keeping the material consumption at a minimum is important for a wide range of Si-based technologies, spanning from batteries to sensors and solar cells. In this work, we elucidate the effects of electron beam deposition (e-beam) conditions on the growth of ~4 µm thick Si layers on bare and thermally oxidized (001)-oriented Si substrates. All depositions are performed from a stabilized and refillable melt of broken B-doped wafers and recollected using Si-shields during deposition for recycling. We find that increasing the deposition rate from 0.3 to 23 nm/s at a substrate temperature of 1000 °C reduces the roughness, void fraction, and residual stress of epitaxial Si-on-Si layers. For Si-on-

S i O_{2}

, all films are polycrystalline under the same deposition conditions as for Si-on-Si, with a reduction in void fraction and increase in roughness at higher deposition rates. The residual stress for Si-on-

S i O_{2}

is comparable across all deposition rates >1 nm/s. Furthermore, we measure lower resistivities in the films than in the feedstock for Si-on-Si and higher than the feedstock for Si-on-

S i O_{2}

. While the films become microstructurally denser and less defective at higher deposition rates, the resistivity increases for each next deposition step in the case of multi-step depositions from the same feedstock. Time-of-flight scanning secondary mass spectroscopy measurements show that the films have a significantly higher B-concentration than the feedstock, suggesting B-gettering to the melted region and transferring to the Si film upon the e-beam deposition process. This work demonstrates how electron beam evaporation can be used to recollect and recycle waste Si pieces, bringing important insights into how the deposition parameters influence the quality of the deposited polycrystalline as well as epitaxial thin-to-thick films. Full article

(This article belongs to the Special Issue Functional Thin Films and Coatings: Present Status, Challenges, and a Look Forward)

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17 pages, 12088 KiB

Open AccessArticle

Effect of Temperature and Immersion Time on Corrosion of Pipeline Steel Caused by Sulfate-Reducing Bacteria

by Yulong Wei, Pei Li, Qingwen Liang, Baihong Wu, Junjie Shen, Huifang Jiang and Qingjian Liu

Coatings 2024, 14(7), 807; https://doi.org/10.3390/coatings14070807 - 28 Jun 2024

Viewed by 132

Abstract

Sulfate-reducing bacteria (SRB) are the primary cause of corrosion in oil and gas pipeline steel. To understand how temperature and immersion time affect the SRB-induced corrosion of BG L450OQO-RCB pipe steel, the present study delved into the morphology and elemental composition of corrosion [...] Read more.

Sulfate-reducing bacteria (SRB) are the primary cause of corrosion in oil and gas pipeline steel. To understand how temperature and immersion time affect the SRB-induced corrosion of BG L450OQO-RCB pipe steel, the present study delved into the morphology and elemental composition of corrosion products, corrosion rate, corrosion solution composition, and electrochemical performance at different temperatures (25, 40, and 60 °C) and immersion times (5, 10, and 20 days). During the SRB corrosion of the investigated steel, extracellular polymeric substances (EPSs), iron sulfide, and iron phosphide were produced on the surfaces of the steel samples, along with the calcium carbonate product. Chloride ions in the corrosion solution contributed to the corrosion of steel and the formation of chlorides on steel surfaces. Over time, the quantities of EPSs, iron sulfide, and iron phosphide gradually decreased with immersion time. The presence of surface iron chloride initially increased and then decreased with immersion time. Conversely, the presence of calcium carbonate surface product initially decreased and then increased with immersion time. The content of SRB extracellular polymer, iron sulfide, and iron phosphide changed imperceptibly between 25 and 40 °C, but the overall content decreased at 60 °C. The content of surface ferric chloride remained practically unchanged between 25 and 40 °C but increased at 60 °C. The calcium carbonate surface product increased slightly with higher temperature. The corrosion of Cu-containing steel by SRB follows the cathodic depolarization theory. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings, 2nd Edition)

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14 pages, 6828 KiB

Open AccessArticle

Research on Micro-Triangular Pyramid Array-Based Fly-Cutting Technology Using the Orthogonal Test Method

by Jiashun Gao, Yu Lei and Zhilong Xu

Coatings 2024, 14(7), 806; https://doi.org/10.3390/coatings14070806 - 28 Jun 2024

Viewed by 130

Abstract

The copper mold of the micro-triangular pyramid (MTP) is a key component of MTP plastic film manufacturing, and its optical functional surface comprises micro-triangular pyramid arrays (MTPAs). The edge burrs of MTPAs severely affect the optical properties of MTP plastic film. To solve [...] Read more.

The copper mold of the micro-triangular pyramid (MTP) is a key component of MTP plastic film manufacturing, and its optical functional surface comprises micro-triangular pyramid arrays (MTPAs). The edge burrs of MTPAs severely affect the optical properties of MTP plastic film. To solve the problem of excessive edge burr of MTPA machining using the fly-cutting method, the orthogonal experimental method was used to optimize the four influencing factors: fly-cutting speed, feed speed, cutting depth, and cooling mode. The results show that the impact of these influencing factors on surface roughness, the projected area of the exit edge burr, and exit edge burr thickness are ranked from largest to the smallest as follows: fly-cutting speed, feed speed, cutting depth, and cooling mode. The factors affecting tool nose wear in descending order are fly-cutting speed, feed speed, cooling mode, and cutting depth. The optimal conditions for minimizing the thickness of the edge burr were a fly-cutting speed of 7.85 m/s, a feed speed of 50 mm/min, a finishing cutting depth of 15 μm, and using compressed air with oil mist for cooling. This study lays a foundation for improving the anti-reflection performance of MTP plastic film. Full article

(This article belongs to the Section Tribology)

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28 pages, 11580 KiB

Open AccessArticle

Durable and High-Temperature-Resistant Superhydrophobic Diatomite Coatings for Cooling Applications

by José Pereira, Reinaldo Souza, António Moreira and Ana Moita

Coatings 2024, 14(7), 805; https://doi.org/10.3390/coatings14070805 - 28 Jun 2024

Viewed by 124

Abstract

The present work is aimed at the development of superhydrophobic coatings and surfaces with enhanced robustness and boiling temperature resistance. We will address the synthesis method of the coatings, which was based on the preparation of a composite of silanized diatomite particles embedded [...] Read more.

The present work is aimed at the development of superhydrophobic coatings and surfaces with enhanced robustness and boiling temperature resistance. We will address the synthesis method of the coatings, which was based on the preparation of a composite of silanized diatomite particles embedded in epoxy resin. After the synthesis of the composite solution, it was applied by dip-coating in stainless steel substrates and submitted to a post-treatment cure in an oven. The method proved to be a comparatively fast and simple one. Then, the substrate/coating sets were characterized using different techniques, including Fourier transform infrared spectroscopy and scanning electron microscopy, and their water contact angle and roughness were measured. Apart from this, the physical and chemical robustness of the sets was also tested using diverse resistance tests like adhesion strength, abrasion resistance, resistance to strong acids and bases, and resistance to boiling water. The main results are that we obtained robust coatings, with wettability defined by water contact angles above 150°. Also, the synthesized coatings revealed good resistance to boiling water, as their properties were almost unchanged after the completion of a long period of tests. The characterization of the produced coatings suggested their propensity to be explored for use in water boiling surfaces and interfaces for cooling purposes in boiling heat transfer systems. Full article

(This article belongs to the Special Issue Research Progress and Application of Super-hydrophobic Anti-icing Surface)

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19 pages, 15244 KiB

Open AccessArticle

Surface Quality of High-Concentration SiC/Al Grinding with Electroassisted Biolubricant MQL

by Weidong Zhang, Dongzhou Jia, Min Yang, Qi Gao, Teng Gao, Zhenjing Duan and Da Qu

Coatings 2024, 14(7), 804; https://doi.org/10.3390/coatings14070804 - 28 Jun 2024

Viewed by 123

Abstract

SiC/Al composites are widely used in aerospace and other fields due to their excellent mechanical properties. For large-concentration composites, due to the extremely high proportion of SiC and the unstable interface between the two phases, the SiC particles are broken and detached during [...] Read more.

SiC/Al composites are widely used in aerospace and other fields due to their excellent mechanical properties. For large-concentration composites, due to the extremely high proportion of SiC and the unstable interface between the two phases, the SiC particles are broken and detached during the processing, which makes the surface quality of the workpiece insufficient to meet the service requirements. Electrically assisted cutting technology is expected to break through this technical bottleneck. This paper investigates the surface quality of high-concentration SiC/Al grinding with electroassisted biolubricant MQL. The surface morphology after processing is observed. Firstly, by comparing the traditional grinding and electrically assisted grinding conditions, it is found that the fundamental reason for the improvement in the grinding surface quality using a pulse current is the improvement in the Al plasticity. Secondly, based on the thermal effect and non-thermal effect of the pulse current, the influence of the electrical parameters (current, duty cycle and frequency) on the machining indication quality is discussed. It is found that when the current and duty cycle increase, the machining surface quality will also increase, while the frequency change has little effect on the surface quality. Finally, friction and wear experiments are carried out on the grinding surface under different working conditions to explore the friction and wear characteristics of the surface of the workpiece. The results show that the pulse current can significantly improve the wear resistance of the grinding surface. Full article

(This article belongs to the Special Issue Biolubricants: Synthesis, Properties, Applications and Future Prospects)

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16 pages, 3276 KiB

Open AccessArticle

Interfacial Behavior of Copper/Steel Bimetallic Composites Fabricated by CMT-WAMM

by Yan Liu, Bo Li, Wenguang Zhang, Zhaozhen Liu and Maofa Jiang

Coatings 2024, 14(7), 803; https://doi.org/10.3390/coatings14070803 - 27 Jun 2024

Viewed by 183

Abstract

Copper/steel bimetallic composites were made by using cold metal transfer wire and arc additive manufacturing (CMT-WAAM) with 1.2 mm diameter ER120S-G high-strength steel and 1.2 mm diameter ERCuSi-A silicon bronze welding wires. Based on the optimal tensile strength, the optimal CMT additive parameters [...] Read more.

Copper/steel bimetallic composites were made by using cold metal transfer wire and arc additive manufacturing (CMT-WAAM) with 1.2 mm diameter ER120S-G high-strength steel and 1.2 mm diameter ERCuSi-A silicon bronze welding wires. Based on the optimal tensile strength, the optimal CMT additive parameters of the copper layer were determined by the single-factor method under the conditions of the fixed steel layer process parameters of a 100 A welding current and 550 mm/min welding speed. The interfacial behavior of copper/steel bimetallic composites with the optimum parameters was investigated in particular. The results show that the optimum CMT additive process parameters for depositing a copper layer on a steel layer are a welding current of 100 A and a welding speed of 500 mm/min. The steel side consists mainly of martensite and ferrite, and the copper side consists of α-Cu matrix, Cu₃Si, and Cu₁₅Si₄ reinforcing phases. The composite interfacial region is mainly composed of the FeSi₂reinforcing phase. At the optimum parameters, the ultimate tensile strength of the composites can reach 404 MPa with a ductile fracture on the copper side. Under the optimum parameters, the microhardness of the composites declines gradually from the steel side to the copper side, and the microhardness at the interface is higher than that at copper side, reaching 190 HV. In addition, the corrosion current density of the copper-side metal is 2.035 × 10⁻⁶ A·cm⁻², and the corrosion current density of the steel-side metal is 7.304 × 10⁻⁶ A·cm⁻². The corrosion resistance of the copper-side metal is higher than that of the steel-side metal. The CMT-WAAM process can produce copper/steel bimetallic composites with excellent comprehensive performance. The advantage of material integration makes it a broad application prospect. Full article

(This article belongs to the Special Issue Microstructure, Mechanical and Tribological Properties of Alloys)

14 pages, 1669 KiB

Open AccessArticle

Research on Drag Reduction by Coating the Inner Wall of Hydraulic Pipeline

by Xue Wang, Junjie Zhou, Wenbo Liao and Shihua Yuan

Coatings 2024, 14(7), 802; https://doi.org/10.3390/coatings14070802 - 27 Jun 2024

Viewed by 180

Abstract

This study employs computational fluid dynamics (CFD) simulations to investigate the effect of wall roughness on linear loss in circular pipelines. It specifically addresses hemispherical roughness, focusing on how changes in spacing influence linear loss, a critical determinant of fluid motion within pipelines. [...] Read more.

This study employs computational fluid dynamics (CFD) simulations to investigate the effect of wall roughness on linear loss in circular pipelines. It specifically addresses hemispherical roughness, focusing on how changes in spacing influence linear loss, a critical determinant of fluid motion within pipelines. The simulations further assess the impact of these variables on flow characteristics, laying a theoretical groundwork for drag reduction and pipeline design improvement. Results indicate that increased spacing between roughness elements reduces the differential pressure at both pipeline ends. The dimensionless spacing value of 30 stabilizes this pressure, suggesting a limit to further changes. Additionally, a rise in roughness height at this spacing exacerbates differential pressure, highlighting a proportional relationship between roughness dimensions and linear loss—greater roughness leads to higher linear loss. Applying a nickel-plated coating on the inner wall significantly lowers roughness, thereby reducing linear loss. Full article

(This article belongs to the Special Issue Surface Science of Degradation and Surface Protection)

8 pages, 2587 KiB

Open AccessCommunication

Energy Storage Performance of (Na_0.5Bi_0.5)TiO₃ Relaxor Ferroelectric Film

by Xuxia Liu, Yao Yao, Xiaofei Wang, Lei Zhao and Xingyuan San

Coatings 2024, 14(7), 801; https://doi.org/10.3390/coatings14070801 - 27 Jun 2024

Viewed by 188

Abstract

Abstract: The (Na_0.5Bi_0.5)TiO₃relaxor ferroelectric materials have great potential in high energy storage capacitors due to their small hysteresis, low remanent polarization and high breakdown electric field. In this work, (Na_0.5Bi_0.5)TiO₃ thin films [...] Read more.

Abstract: The (Na_0.5Bi_0.5)TiO₃relaxor ferroelectric materials have great potential in high energy storage capacitors due to their small hysteresis, low remanent polarization and high breakdown electric field. In this work, (Na_0.5Bi_0.5)TiO₃ thin films with ~400 nm were prepared on (001) SrTiO₃ substrate by pulsed laser deposition technology. The (Na_0.5Bi_0.5)TiO₃films have good crystallization quality with a dense microstructure and relaxor ferroelectric properties, as confirmed by the elongated hysteresis loops and the relation of <A>∝E^α. A high E_b of up to 1400 kV/cm is obtained, which contributes to a good W_rec of 24.6 J/cm³and η of 72% in (Na_0.5Bi_0.5)TiO₃ film. In addition, the variations of W_rec and η are less than 4% and 10% in the temperature range of 20–120°C. In the frequency range of 10³Hz–2 × 10⁴Hz, the variations of W_rec and η are less than 10%. All those reveal the great potential of NBT film for energy storage. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

13 pages, 2408 KiB

Open AccessArticle

Characterization of Materials Used in the Concrete Industry, from the Point of View of Corrosion Behavior

by Marius Gabriel Petrescu, Razvan George Ripeanu, Eugen Laudacescu, Maria Tanase, Adrian Niță and Andrei Burlacu

Coatings 2024, 14(7), 800; https://doi.org/10.3390/coatings14070800 - 27 Jun 2024

Viewed by 234

Abstract

Industrial applications in the concrete industry face significant challenges in selecting appropriate metallic materials, as these choices can enhance equipment lifespan and reduce costs. This study examines the corrosion behavior of various metallic materials, offering valuable insights for their selection in corrosive environments. [...] Read more.

Industrial applications in the concrete industry face significant challenges in selecting appropriate metallic materials, as these choices can enhance equipment lifespan and reduce costs. This study examines the corrosion behavior of various metallic materials, offering valuable insights for their selection in corrosive environments. The findings indicate that material testing can provide cost-effective solutions for concrete industry equipment. Notably, replacing cast iron used in concrete mixing blades with specific steels is advantageous for corrective or accidental maintenance, lowering spare parts costs, and short-term use, steels P265GH and AISI 4140 exhibiting corrosion resistance similar to cast iron. Additionally, for mineral aggregate dryers, selecting adequate steel can significantly reduce operating and maintenance costs while increasing equipment durability. The results show that substituting steel S235 with steel P265GH can decrease the corrosion rate by nearly 65%. Full article

(This article belongs to the Special Issue Green and Low-Carbon Buildings: Materials, Technology and Processes and Techniques)

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16 pages, 1357 KiB

Open AccessArticle

Design of a Far-Infrared Broadband Metamaterial Absorber with High Absorption and Ultra-Broadband

by Tao Xu, Yingting Yi, Qianju Song, Zao Yi, Yougen Yi, Shubo Cheng, Jianguo Zhang, Chaojun Tang, Tangyou Sun and Qingdong Zeng

Coatings 2024, 14(7), 799; https://doi.org/10.3390/coatings14070799 - 26 Jun 2024

Viewed by 135

Abstract

We designed a metamaterial far-infrared absorber based on an MDM (metal–dielectric–metal) structure. We made a hollow crossed Ti microstructure at the top of the absorber. It is known that the coupling effect of equipartitional exciton resonance and intrinsic absorption at the surface of [...] Read more.

We designed a metamaterial far-infrared absorber based on an MDM (metal–dielectric–metal) structure. We made a hollow crossed Ti microstructure at the top of the absorber. It is known that the coupling effect of equipartitional exciton resonance and intrinsic absorption at the surface of the depleting material has a strong influence on the absorber. Based on this, we investigated the absorption characteristics of the absorber using the Finite Difference in Time Domain (FDTD) theory. The results show that the absorber absorbed more than 90% of the light within a bandwidth of 12.01 μm. The absorber has an average absorption of 94.08% in the longwave infrared (LWIR) to ultra-longwave infrared (UWIR) bands (10.90–22.91 μm). The polarization insensitivity of the designed absorber is demonstrated by analyzing the absorption spectra of the absorber at different polarization angles. By adjusting the relevant geometric parameters, the absorption spectrum can be independently adjusted. Furthermore, the absorber exhibits good incidence angle insensitivity in both transverse electric (TE) and transverse magnetic (TM) modes. The absorbers are simple and easy to configure for applications such as optical cloaking, infrared heat emitters, and photodetectors. These advantages will greatly benefit the application of absorbers in practice. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

14 pages, 1106 KiB

Open AccessArticle

Duplex Surface Modification of M2 High-Speed Steel

by Maria Ormanova, Georgi Kotlarski, Dimitar Dechev, Nikolay Ivanov, Borislav Stoyanov and Stefan Valkov

Coatings 2024, 14(7), 798; https://doi.org/10.3390/coatings14070798 - 26 Jun 2024

Viewed by 120

Abstract

In this investigation, a duplex surface modification of M2 high-speed steel (HSS) was demonstrated, including electron beam treatment (EBT) followed by a tungsten nitride (WN) coating deposition. The influence of the EBT of the substrate on the functional properties of the film was [...] Read more.

In this investigation, a duplex surface modification of M2 high-speed steel (HSS) was demonstrated, including electron beam treatment (EBT) followed by a tungsten nitride (WN) coating deposition. The influence of the EBT of the substrate on the functional properties of the film was also studied. The phase composition of the EBT sample consists of Fe (the main element in the M2 HSS), as well as MC and M₆C carbides, while the phase composition of the EBT + WN sample consists of the α’-Fe, M₆C, and WN phases. The depth of the treated zone is about 20 μm, and the thickness of the WN coating is about 300 nm in all cases. The hardness of the coating deposited on the EBT substrate is 12.4 GPa, while that of the WN film deposited on the untreated substrate is 8.8 GPa. The application of the electron beam treatment procedure and deposition of WN film leads to an improvement in the tribological properties where the coefficient of friction decreases from 0.81 to 0.66. However, the same coating deposited on untreated substrate exhibits even less friction coefficient values of 0.54. The applied modification technique suggests that this is a viable method for improving the mechanical and tribological properties of the surface of tool steels and, thus, their longevity and applicability. Full article

(This article belongs to the Special Issue Surface Modification of Magnesium, Aluminum Alloys, and Steel)

9 pages, 2561 KiB

Open AccessArticle

Experimental and Adsorption Kinetics Study of Hg⁰ Removal from Flue Gas by Silver-Loaded Rice Husk Gasification Char

by Ru Yang, Yongfa Diao, Hongbin Liu and Yihang Lu

Coatings 2024, 14(7), 797; https://doi.org/10.3390/coatings14070797 - 26 Jun 2024

Viewed by 189

Abstract

Coal holds a significant position in China’s energy consumption structure. However, the release of Hg⁰ during coal combustion poses a serious threat to human health. Traditional activated carbon for Hg⁰ removal is expensive; finding efficient, inexpensive and renewable adsorbents for Hg [...] Read more.

Coal holds a significant position in China’s energy consumption structure. However, the release of Hg⁰ during coal combustion poses a serious threat to human health. Traditional activated carbon for Hg⁰ removal is expensive; finding efficient, inexpensive and renewable adsorbents for Hg⁰ removal has become a top priority. Rice husk gasification char (RHGC) is a solid waste generated by biomass gasification power generation, which, loaded with silver to remove Hg⁰, could achieve the purpose of waste treatment. This paper examines the Hg⁰ removal performance of silver-loaded rice husk gasification char (SRHGC) under different operating conditions through experimental analysis. This study employed quasi-first-order, quasi-second-order, and internal diffusion kinetics adsorption equations to model the amount of Hg⁰ removed by SRHGC at different temperatures, thereby inferring the reaction mechanism. The results indicate that Hg⁰ removal efficiency of SRHGC increased by about 80%. The Hg⁰ removal ability was directly related to silver load, and the amount of Hg⁰ removed by SRHGC did not a exhibit a simple inverse relationship with particle size. Additionally, the Hg⁰ removal efficiency of SRHGC declined with increasing adsorption temperature. The removal of Hg⁰ by SRHGC conformed to the quasi-second-order kinetic equation, with the adsorption rate constant decreasing as the temperature rose, consistent with experimental observations. This paper provides both experimental and theoretical references for future modification and optimization of RHGC for coal-fired flue gas treatment, and also offers valuable insights into Hg⁰ removal by carbon-based adsorbents. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Performance Enhancement of Electrode and Biomaterial Coatings)

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11 pages, 1923 KiB

Open AccessArticle

Catalytic Activity Evaluation of Molten Salt-Treated Stainless Steel Electrodes for Hydrogen Evolution Reaction in Alkaline Medium

by Michihisa Fukumoto, Hiroki Takahashi, Dawid Kutyła, Marek Wojnicki and Piotr Żabiński

Coatings 2024, 14(7), 796; https://doi.org/10.3390/coatings14070796 - 26 Jun 2024

Viewed by 175

Abstract

The goal of this research is to fabricate a novel type of highly active porous electrode material, based on stainless steel and dedicated to water electrolyzers. The main novelty of the presented work is the innovative application of the molten salts treatment, which [...] Read more.

The goal of this research is to fabricate a novel type of highly active porous electrode material, based on stainless steel and dedicated to water electrolyzers. The main novelty of the presented work is the innovative application of the molten salts treatment, which allows the design of a highly developed porous structure, which characterizes significantly higher catalytic activity than untreated steel substrates. The equimolar mixture of NaCl and KCl with 3.5 mol% AlF₃ was used as the molten salt. The surface modification procedure includes the deposition of an Al layer with application at the potential of −1.8 V and following dissolution at −0.9 V, to create a porous alloy surface. The cathodic polarization measurements of the prepared porous stainless steel electrodes were measured in a 10 mass% KOH solution. Moreover, the amount of hydrogen generated during constant voltage electrolysis with a hydrogen sensor in situ was also measured. The porous stainless steel alloy showed higher current density at lower potentials in the cathodic polarization compared to untreated stainless steel. The cathodic polarization measurements in alkaline solution showed that the porous 304 stainless steel alloy is an excellent cathode material. Full article

(This article belongs to the Special Issue Coatings as Key Materials in Catalytic Applications)

20 pages, 5753 KiB

Open AccessArticle

Wet-Chemical Fabrication of Functional Humidity Sensors on a TiO₂-Coated Glass Substrate via UV Photodeposition

by Bozhidar I. Stefanov

Coatings 2024, 14(7), 795; https://doi.org/10.3390/coatings14070795 - 26 Jun 2024

Viewed by 328

Abstract

This work demonstrates a completely wet-chemical procedure for the fabrication of a functional impedimetric humidity-sensing device on a titania (TiO₂) surface. Optically transparent anatase TiO₂ thin films were deposited on a glass substrate via dip-coating from a titanium tetraisopropoxide (TTIP)–acetylacetonate [...] Read more.

This work demonstrates a completely wet-chemical procedure for the fabrication of a functional impedimetric humidity-sensing device on a titania (TiO₂) surface. Optically transparent anatase TiO₂ thin films were deposited on a glass substrate via dip-coating from a titanium tetraisopropoxide (TTIP)–acetylacetonate (AA)-based sol and surface-functionalized with a nickel oxide (NiO_x) layer by ultraviolet (UV) photodeposition. Photodeposition was employed to form the interdigitated electrode pattern on the TiO₂ surface as well through activation with a silver catalyst to promote electroless copper deposition. The relative humidity (RH) response of the pristine TiO₂- and NiO_x/TiO₂-functionalized sensors was studied by impedance (Z) measurements in the 15%–90% RH range. It was found that while NiO_x functionalization significantly dampens the RH–Z functional dependence, it improves its overall linearity and may successfully be employed for the purposeful design of titania-based sensing devices. Full article

(This article belongs to the Special Issue Functional Thin Films and Coatings: Present Status, Challenges, and a Look Forward)

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13 pages, 3340 KiB

Open AccessArticle

Stable N-Type Single-Walled Carbon Nanotube/Mesh Sheets by Cationic Surfactant Doping and Fluoropolymer Coating for Flexible Thermoelectric Generators

by Takuya Amezawa and Masayuki Takashiri

Coatings 2024, 14(7), 794; https://doi.org/10.3390/coatings14070794 - 26 Jun 2024

Viewed by 154

Abstract

Single-walled carbon nanotubes (SWCNTs) offer promise as materials for thermoelectric generators (TEGs) due to their flexibility, durability, and non-toxic nature. However, a key barrier to their application lies in their high thermal conductivity, which hampers the generation of temperature differences in TEGs. To [...] Read more.

Single-walled carbon nanotubes (SWCNTs) offer promise as materials for thermoelectric generators (TEGs) due to their flexibility, durability, and non-toxic nature. However, a key barrier to their application lies in their high thermal conductivity, which hampers the generation of temperature differences in TEGs. To address this challenge, we explored a method of enhancing the heat dissipation of SWCNT-based TEGs by coating SWCNT layers onto polymer mesh sheets. During TEG fabrication, achieving stable n-type SWCNT/mesh sheets proved considerably more challenging than their p-type counterparts. This difficulty stemmed from the inferior dispersibility of the n-type SWCNT ink compared to the p-type SWCNT ink. To produce n-type SWCNT/mesh sheets, we initially prepared p-type SWCNT/mesh sheets using p-type SWCNT ink, subsequently doping them with a cationic surfactant solution to induce n-type characteristics. To stabilize the n-type thermoelectric properties in SWCNT/mesh sheets, we applied a fluoropolymer coating to the SWCNT surfaces, mitigating the adsorption of oxygen molecules. This approach yielded n-type SWCNT/mesh sheets capable of long-term maintenance. Furthermore, flexible TEGs fabricated using both p- and n-type SWCNT/mesh sheets demonstrated an output voltage of 15 mV, which can operate IoT sensors using the latest booster circuits, and a maximum power of 100 nW at a temperature difference of 71 K. Full article

(This article belongs to the Special Issue Thermoelectric Materials for Sustainable Applications)

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12 pages, 4831 KiB

Open AccessArticle

Lifetime Extension of Atmospheric and Suspension Plasma-Sprayed Thermal Barrier Coatings in Burner Rig Tests by Pre-Oxidizing the CoNiCrAlY Bond Coats

by Jens Igel, Walter Sebastian Scheld, Daniel Emil Mack, Olivier Guillon and Robert Vaßen

Coatings 2024, 14(7), 793; https://doi.org/10.3390/coatings14070793 - 26 Jun 2024

Viewed by 203

Abstract

Oxidation of the bond coat during turbine operation leads to additional stresses in the thermal barrier coating (TBC) system that promotes spalling of the thermal insulation. Therefore, the oxidation behavior of a TBC system plays an important role in the thermal cycling of [...] Read more.

Oxidation of the bond coat during turbine operation leads to additional stresses in the thermal barrier coating (TBC) system that promotes spalling of the thermal insulation. Therefore, the oxidation behavior of a TBC system plays an important role in the thermal cycling of a TBC system. To delay the loss of thermal insulation, research has typically focused for a long time on the composition and microstructure of the ceramic topcoats and metallic bond coats. More recently, heat treatment for the diffusion annealing of the bond coat has also become a focus of research. Several studies have shown that pre-oxidation of the bond coat prior to the application of the ceramic topcoat slows down the subsequent oxidation of the bond coat in service. The improved thermal cyclability has been demonstrated in studies for systems with atmospheric plasma-sprayed (APS), suspension plasma-sprayed (SPS) or electron beam physical vapor deposition (EB-PVD) top coatings. However, no study has directly compared the effects of pre-oxidation on different topcoats. Therefore, this study compared the effect of pre-oxidation on APS and SPS coatings with the same bond coat. For both topcoats, pre-oxidation slowed the subsequent TGO growth and thus increased the lifetime of the coatings. The improvement in lifetime was particularly pronounced for the systems with an SPS topcoat. Overall, the lifetime of the coatings with an APS topcoat was higher as the critical energy release rate within the coating was not exceeded in these coatings. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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18 pages, 1486 KiB

Open AccessArticle

Corrosion Efficiency of Zn-Ni/ZrO₂ and Zn-Co/ZrO₂ Bi-Layer Systems: Impact of Zn-Alloy Sublayer Thickness

by Nelly Boshkova, Daniela Stoyanova, Irina Stambolova, Ognian Dimitrov, Sylviya Simeonova, Georgi Avdeev, Miglena Peshova, Vasil Bachvarov, Sonya Smrichkova and Nikolai Boshkov

Coatings 2024, 14(7), 792; https://doi.org/10.3390/coatings14070792 - 25 Jun 2024

Viewed by 295

Abstract

The presented manuscript demonstrates the effect of the thickness of a zinc alloy sublayer on the corrosion resistance and stability of three types of bi-layer systems composed of Co- or Ni-modified zinc coatings (both as sublayers) and a top sol–gel ZrO₂film [...] Read more.

The presented manuscript demonstrates the effect of the thickness of a zinc alloy sublayer on the corrosion resistance and stability of three types of bi-layer systems composed of Co- or Ni-modified zinc coatings (both as sublayers) and a top sol–gel ZrO₂film in a 5% NaCl solution. In order to obtain more detailed information, the alloy sublayers were electrodeposited with three different thicknesses (1, 5 and 10 µm, respectively) on a low-carbon steel substrate. Three consecutive dip-coated ZrO₂ sol–gel layers were deposited thereafter on the individual zinc alloy sublayers. For comparison, an ordinary electrodeposited zinc coating was obtained and investigated. The aim of this study was to evaluate the effect of the thickness of the zinc-based sublayer on the protective characteristics of the bi-layer systems. The surface morphology features and the phase composition of the latter systems were examined using scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA) measurements and X-ray diffraction (XRD) analyses. The corrosion stability was evaluated by means of potentiodynamic polarization (PDP) curves and polarization resistance (Rp) measurements. The zirconia finish layers possessed an amorphous, dense and hydrophobic nature, while the sublayers were multicrystalline. The results confirmed the increased corrosion resistance of the protective system, which contained the electrodeposited layer on the Zn-Co alloy with a 10 µm thickness in a corrosive test medium. Full article

(This article belongs to the Special Issue Effects of Surface Layer Modification on Fatigue, Corrosion and Wear Behavior of Metallic Materials)

21 pages, 4321 KiB

Open AccessArticle

Analysis of Wear Vibration Behavior of Micro-Textured Coated Cemented Carbide Considering High-Order Scale

by Xin Tong and Shoumeng Wang

Coatings 2024, 14(7), 791; https://doi.org/10.3390/coatings14070791 - 25 Jun 2024

Viewed by 319

Abstract

In order to explore the influence of high-order micro-texture parameters on the friction, wear, and vibration characteristics of coated cemented carbide pin surfaces, expand the research field of textured coating modification processes. Firstly, a laser was used to prepare micro-texture on the surface [...] Read more.

In order to explore the influence of high-order micro-texture parameters on the friction, wear, and vibration characteristics of coated cemented carbide pin surfaces, expand the research field of textured coating modification processes. Firstly, a laser was used to prepare micro-texture on the surface of the cemented carbide pin, and AlCrN coating was carried out. The friction and wear test platform of the micro-textured physical vapor deposition (PVD)-coated cemented carbide and titanium alloy substrate was built, and the friction vibration and acoustic vibration signals were obtained as the main analysis media. Secondly, according to the characteristics of the test signal, three time-frequency images are analyzed and compared. The continuous wavelet transform (CWT) method with a better time-frequency analysis effect is selected. Finally, the characteristics and regularity of friction vibration and acoustic vibration are analyzed by using the gray mean of the CWT time-frequency image. The influence mechanism of high-order micro-texture parameters on the surface characteristics of coated cemented carbide pins was obtained. It is concluded that the high-order micro-texture is 1.58% higher than the traditional scale in the stability of friction vibration, 4.47% higher in the stability of acoustic vibration, and 13.16% lower in the friction force, which proves the progress of the size improvement. It provides a practical basis for the extension research of cemented carbide surface modification. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

18 pages, 5365 KiB

Open AccessArticle

Change of Adhesion Properties of Bioinspired Laser-Induced Periodic Nanostructures towards Cribellate Spider Nanofiber Threads by Means of Thin Coatings

by Johannes Heitz, Gerda Buchberger, Werner Baumgartner, Marco Meyer, Margret Weissbach, Anna-Christin Joel, Simona Brajnicov, Alexandra Palla-Papavlu and Maria Dinescu

Coatings 2024, 14(7), 790; https://doi.org/10.3390/coatings14070790 - 25 Jun 2024

Viewed by 653

Abstract

We investigated the effect of additional continuous functional coatings, which changed the hydrophilic–hydrophobic properties of the surface without heavily influencing the surface topography at the nanoscale, on the antiadhesive properties of bioinspired laser-induced periodic nanostructures. These nanostructures mimic the antiadhesive structures on the [...] Read more.

We investigated the effect of additional continuous functional coatings, which changed the hydrophilic–hydrophobic properties of the surface without heavily influencing the surface topography at the nanoscale, on the antiadhesive properties of bioinspired laser-induced periodic nanostructures. These nanostructures mimic the antiadhesive structures on the silk-combing area on the legs of cribellate spiders, the calamistrum. The thin films were deposited by matrix-assisted laser deposition and characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurements, and adhesion tests using capture threads from the cribellate spider webs. In all cases, the nanoripples were preserved and these structured surfaces showed lower adhesion forces compared to flat controls, although not significant. However, this effect was totally overwhelmed by the difference between the adhesion forces on surfaces with different chemical compositions. The largest adhesion forces were observed on hydrophilic surfaces and the lowest ones on hydrophobic surfaces. The fact that the antiadhesion between nanofibers and the nano-structured areas depends strongly on the chemical composition of the surface can be explained by the specific adhesion between individual chemical groups due to frequency dependencies in the theory of van der Waals forces. However, explaining these adhesion properties just by the categories “hydrophilic” or “hydrophobic” is oversimplified. Full article

(This article belongs to the Special Issue Smart Coatings)

14 pages, 4574 KiB

Open AccessArticle

Research on Fatigue Performance of Fast-Melting SBS/Epoxy Resin Composite-Modified Asphalt

by Bo Men, Xiaoyu Li, Tianyu Sha, Fei Guo, Guoqi Tang and Jinchao Yue

Coatings 2024, 14(7), 789; https://doi.org/10.3390/coatings14070789 - 25 Jun 2024

Viewed by 217

Abstract

A high-performance composite modifier ER-SBS-T was prepared through the mixing of epoxy resin with a fast-melting styrene–butadiene–styrene modifier (SBS-T) to enhance material properties. This study evaluated the fatigue characteristics of ER-SBS-T-modified asphalt using a linear amplitude sweep test, and 70# base asphalt, SBS-modified [...] Read more.

A high-performance composite modifier ER-SBS-T was prepared through the mixing of epoxy resin with a fast-melting styrene–butadiene–styrene modifier (SBS-T) to enhance material properties. This study evaluated the fatigue characteristics of ER-SBS-T-modified asphalt using a linear amplitude sweep test, and 70# base asphalt, SBS-modified asphalt, and SBS-T-modified asphalt were used as control groups. The fatigue life of ER-SBS-T-modified asphalt was determined according to viscoelastic continuous damage (VECD) theory. The findings indicated that as the ER-SBS-T modifier content increased, both the maximum value and the cumulative damage limit value increased, while the rate of change of decreased. At strain levels of 2.5% and 1%, the fatigue life of the modified asphalt improved with increasing ER-SBS-T content. However, at a strain level of 5%, the modified asphalt exhibited no significant trend in fatigue life across different ER-SBS-T contents. ER-SBS-T-modified asphalt with a modifier content of >10% demonstrated favorable fatigue performance suitable for practical engineering applications. Full article

(This article belongs to the Special Issue Development and Characterization of New Construction Materials and Coatings)

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18 pages, 7606 KiB

Open AccessArticle

Symbiosis of Sulfate-Reducing Bacteria and Total General Bacteria Affects Microbiologically Influenced Corrosion of Carbon Steel

by Juxing Jin, Yingchao Li, Huaiwei Huang, Yong Xiang and Wei Yan

Coatings 2024, 14(7), 788; https://doi.org/10.3390/coatings14070788 - 24 Jun 2024

Viewed by 300

Abstract

The effects of the symbiosis of sulfate-reducing bacteria (SRB) and total general bacteria (TGB) on the microbiologically influenced corrosion (MIC) of carbon steel were investigated in this research. The SRB was the main corrosive bacterium, and TGB induced slightly general MIC. The symbiosis [...] Read more.

The effects of the symbiosis of sulfate-reducing bacteria (SRB) and total general bacteria (TGB) on the microbiologically influenced corrosion (MIC) of carbon steel were investigated in this research. The SRB was the main corrosive bacterium, and TGB induced slightly general MIC. The symbiosis of SRB and TGB induced more severe MIC and pitting corrosion than SRB. The main corrosion products were FeS, Fe₂O₃, and FeOOH. The presence of TGB facilitates MIC and pitting corrosion by providing a locally anaerobic shelter for SRB. An MIC mechanism of the symbiosis of SRB and TGB was proposed. Full article

(This article belongs to the Special Issue Investigation on Structure and Corrosion Resistance of Steels/Alloys)

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28 pages, 9190 KiB

Open AccessReview

Plasma-Sprayed Osseoconductive Hydroxylapatite Coatings for Endoprosthetic Hip Implants: Phase Composition, Microstructure, Properties, and Biomedical Functions

by Robert B. Heimann

Coatings 2024, 14(7), 787; https://doi.org/10.3390/coatings14070787 - 24 Jun 2024

Viewed by 271

Abstract

This contribution attempts to provide a state-of-the-art account of the physicochemical and biomedical properties of the plasma-sprayed hydroxylapatite (HAp) coatings that are routinely applied to the surfaces of metallic endoprosthetic and dental root implants designed to replace or restore the lost functions of [...] Read more.

This contribution attempts to provide a state-of-the-art account of the physicochemical and biomedical properties of the plasma-sprayed hydroxylapatite (HAp) coatings that are routinely applied to the surfaces of metallic endoprosthetic and dental root implants designed to replace or restore the lost functions of diseased or damaged tissues of the human body. Even though the residence time of powder particles of HAp in the plasma jet is extremely short, the high temperature applied induces compositional and structural changes in the precursor HAp that severely affect its chemical and physical properties and in turn its biomedical performance. These changes are based on the incongruent melting behavior of HAp and can be traced, among many other analytical techniques, by high resolution synchrotron X-ray diffraction, vibrational (Raman) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In vivo reactions of the plasma-sprayed coatings to extracellular fluid (ECF) can be assessed and predicted by in vitro testing using simulated body fluids (SBFs) as proxy agents. Ways to safeguard the appropriate biological performance of HAp coatings in long-term service by controlling their phase content, porosity, surface roughness, residual stress distribution, and adhesion to the implant surface are being discussed. Full article

(This article belongs to the Special Issue Advanced Biomaterials and Coatings)

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23 pages, 6499 KiB

Open AccessReview

A Review of Research on Improving Wear Resistance of Titanium Alloys

by Yazhou Chen, Honggang Zhang, Bitao Wang, Jianyong Huang, Meihong Zhou, Lei Wang, Yuntao Xi, Hongmin Jia, Shanna Xu, Haitao Liu, Lei Wen, Xinke Xiao, Ruifan Liu and Jiangtao Ji

Coatings 2024, 14(7), 786; https://doi.org/10.3390/coatings14070786 - 24 Jun 2024

Viewed by 322

Abstract

Titanium alloy is widely used as oil drill pipe material because of its light weight, high strength, good toughness, corrosion resistance, fatigue resistance, and good process performance. However, due to its low hardness, poor wear resistance, serious oxidation at high temperature (700 °C), [...] Read more.

Titanium alloy is widely used as oil drill pipe material because of its light weight, high strength, good toughness, corrosion resistance, fatigue resistance, and good process performance. However, due to its low hardness, poor wear resistance, serious oxidation at high temperature (700 °C), and difficulty in lubrication, in oil and gas field exploration and development drilling, especially in deep wells, high displacement wells, horizontal wells, and highly deviated wells, wear and tear are prone to occur. The application and development of titanium alloys are greatly limited. This paper introduces the research status of the common surface modification technologies of titanium alloys, such as laser cladding, magnetron sputtering, plasma spraying, micro arc oxidation, etc. It points out the improvement effect of various modification technologies on the wear resistance and high-temperature oxidation resistance of titanium alloys and discusses the advantages and disadvantages of various modification technologies. A proposed method for enhancing the wear resistance and high-temperature oxidation resistance of titanium alloys was finally introduced, and its potential for future development was investigated. Full article

(This article belongs to the Special Issue Anti-corrosion and Anti-wear Coatings: Fundamentals, Technologies, and Applications)

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23 pages, 6897 KiB

Open AccessArticle

Design and Performance Study of Carbon Fiber-Reinforced Polymer Connection Structures with Surface Treatment on Aluminum Alloy (6061)

by Jianxin Zhang, Yang Liu, Lele Cheng, Dongxu Kang, Ruize Gao, Yinle Qin, Zhonghao Mei, Mengshuai Zhang, Muhuo Yu and Zeyu Sun

Coatings 2024, 14(7), 785; https://doi.org/10.3390/coatings14070785 - 23 Jun 2024

Viewed by 276

Abstract

The existing connection methods for aluminum alloy profiles primarily include adhesive bonding and mechanical connections, with metal welding being widely employed. However, metal welding connections exhibit issues such as low joint strength, significant welding deformation, susceptibility to surface oxidation, poor welding surface quality, [...] Read more.

The existing connection methods for aluminum alloy profiles primarily include adhesive bonding and mechanical connections, with metal welding being widely employed. However, metal welding connections exhibit issues such as low joint strength, significant welding deformation, susceptibility to surface oxidation, poor welding surface quality, and challenges in achieving thin-walled metal structures. This paper presents a novel aluminum alloy connection structure that utilizes carbon fiber-reinforced polymer (CFRP) composites to replace welding for connecting aluminum alloy profiles. This innovative aluminum alloy composite connection structure not only enhances connection strength but also addresses the difficulties associated with metal welding. Research indicates that the optimal width of the CFRP structure in the connector is 60 mm, and with synergistic treatment of the aluminum alloy surface, the connection enhancement effect is optimal. Under these conditions, the tensile load can reach 58.71 kN and the bending load can reach 14.33 kN, which are 375.38% and 380.87% higher than those of welded aluminum alloy connections, respectively. The mass-specific strength increases by 106.27% and 134.42%, respectively. Simulations of this connection structure in components demonstrate that it improves strength by 73.99% and mass-specific strength by 71.95% compared to pure metal welded connections. Using ABAQUS 2023 software for simulation and calculation, the difference between the simulation and experimental results is within 5%, verifying the feasibility of the designed structure. This study provides new insights and a theoretical foundation for the development and application of hybrid connection methods involving metal and fiber-reinforced composites. Full article

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Coatings, Volume 14, Issue 7 (July 2024) – 37 articles

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