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Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications

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A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Surface Characterization, Deposition and Modification".

Deadline for manuscript submissions: closed (23 July 2024) | Viewed by 16731

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Prof. Dr. Hongbo Ju

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School of Material Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang, China
Interests: PVD; hard coatings; tribological properties; 3D
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Dr. Bingyang Ma

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School of Materials Science and Engineering, Shanghai Dianji University, Shanghai 201306, China
Interests: coatings; PVD sputtering; mechanical and tribological performances
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Prof. Dr. Yuxin Wang

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School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Interests: corrosion & surface protection; rapid solidification & powder metallurgy; microstructure & micro-defects of materials; magnetic materials
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Dr. Filipe Fernandes

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CIDEM, ISEP—Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 4249-015 Porto, Portugal
Interests: hard coatings; machining; materials characterization; corrosion
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Special Issue Information

Dear Colleagues,

The overwhelming scientific consensus is that the excessive consumption of energy is a key component in climate change and that friction and wear are major players in energy consumption. In this regard, coating technology is one of the most effective techniques for enhancing the surface performance of tribological components due to its ability to either induce self-lubrication or replace traditional liquid lubricants, and also improves the wear resistance to prolong durability. Therefore, the latest research on hard coatings is critical for engineers and researchers in this research field.

This Special Issue of Coatings,“Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications”, aims to cover original research and critical review articles on recent advances in system hard coatings and their applications. The scope of this issue includes, but is not limited to:

Fundamentals and new surface technology designs;
Hard coatings for cutting tools;
Self-lubricant coatings for critical applications to reduce wear and/or friction;
Advanced characterization techniques for hard coatings
Simulation of the microstructure and performances of hard coatings.

Dr. Hongbo Ju
Dr. Bingyang Ma
Prof. Dr. Yuxin Wang
Dr. Filipe Fernandes
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

surface technologies
hard coatings
nano-structured
simulation
tribology
machining

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Published Papers (10 papers)

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Research

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13 pages, 6471 KiB

Open AccessArticle

Fabrication and Tribological Properties of Diamond-like Carbon Film with Cr Doping by High-Power Impulse Magnetron Sputtering

by Shuai Liu, Wenjian Zhuang, Jicheng Ding, Yuan Liu, Weibo Yu, Ying Yang, Xingguang Liu, Jing Yuan and Jun Zheng

Coatings 2024, 14(7), 916; https://doi.org/10.3390/coatings14070916 - 22 Jul 2024

Viewed by 697

Abstract

The present study aims to investigate the advantages of diamond-like carbon (DLC) films in reducing friction and lubrication to address issues such as the low surface hardness, high friction coefficients, and poor wear resistance of titanium alloys. Cr-doped DLC films were deposited by high-power impulse magnetron sputtering (HiPIMS) in an atmosphere of a gas mixture of Ar and C₂H₂. The energy of the deposited particles was controlled by adjusting the target powers, and four sets of film samples with different powers (4 kW, 8 kW, 12 kW, and 16 kW) were fabricated. The results showed that with an increase in target power, the Cr content increased from 3.73 at. % to 22.65 at. %; meanwhile, the microstructure of the film evolved from an amorphous feature to a nanocomposite structure, with carbide embedded in an amorphous carbon matrix. The sp²-C bond content was also increased in films, suggesting an intensification of the film’s graphitization. The hardness of films exhibited a trend of initially increasing and then decreasing, reaching the maximum value at 12 kW. The friction coefficient and wear rate of films showed a reverse trend compared to hardness variation, namely initially decreasing and then increasing. The friction coefficient reached a minimum value of 0.14, and the wear rate was 2.50 × 10⁻⁷ (mm³)/(N·m), at 8 kW. The abrasive wear was the primary wear mechanism for films deposited at a higher target power. Therefore, by adjusting the target power parameter, it is possible to control the content of the metal and sp²/sp³ bonds in metal-doped DLC films, thereby regulating the mechanical and tribological properties of the films and providing an effective approach for addressing surface issues in titanium alloys. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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12 pages, 7564 KiB

Open AccessArticle

Development and Mechanical Characterization of Ni-Cr Alloy Foam Using Ultrasonic-Assisted Electroplating Coating Technique

by Raj Kumar Pittala, Priyaranjan Sharma, Gajanan Anne, Sachinkumar Patil, Vinay Varghese, Sudhansu Ranjan Das, Ch Sateesh Kumar and Filipe Fernandes

Coatings 2023, 13(6), 1002; https://doi.org/10.3390/coatings13061002 - 28 May 2023

Viewed by 2016

Abstract

Metal foams and alloy foams are a novel class of engineering materials and have numerous applications because of their properties such as high energy absorption, light weight and high compressive strength. In the present study, the methodology adopted to develop a Ni-Cr alloy foam is discussed. Polyurethane (PU) foam of 40PPI (parts per inch) pore density was used as the precursor and coating techniques such as electroless nickel plating (ELN), ultrasonic-assisted electroplating of nickel (UAEPN), and pack cementation or chromizing were used to develop the Ni-Cr alloy foam. The surface morphology, strut thickness and minimum weight gain after each coating stage were evaluated. It was observed from the results that the adopted coating techniques did not damage the original ligament cross-section of the PU precursor. The minimum weight gain and the coating thickness after the UAEPN process were observed to be 42 g and 40–60 μm, respectively. The properties such as porosity percentage, permeability and compressive strength were evaluated. Finally, the pressure drop through the developed foam was estimated and verified to determine whether the developed foam can be used for filtering applications. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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19 pages, 4576 KiB

Open AccessArticle

Comparative Evaluation of Coated Carbide and CBN Inserts Performance in Dry Hard-Turning of AISI 4140 Steel Using Taguchi-Based Grey Relation Analysis

by Mustafa Özdemir, Mohammad Rafighi and Mohammed Al Awadh

Coatings 2023, 13(6), 979; https://doi.org/10.3390/coatings13060979 - 24 May 2023

Cited by 3 | Viewed by 1572

Abstract

Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM and ANOVA. In addition, multi-objective optimization (Grey Relation Analysis: GRA) is performed to determine the optimum machining parameters. Dry hard-turning tests were carried out on AISI 4140 steel (50 HRC) using coated carbide and CBN inserts with different nose radii. The results show that the cutting force components are greatly affected by the cutting depth and cutting speed for both cutting inserts. As the level of cutting depth and cutting speed rise, the cutting forces also increase. However, the feed rate was the main factor in surface roughness. A low feed rate and high cutting speed lead to good surface quality. According to the results, CBN inserts exhibited better performance compared to carbide inserts in terms of minimum cutting forces and surface roughness. The lowest radial force (Fx = 55.59 N), tangential force (Fy = 15.09 N), cutting force (Fz = 30.49 N), and best surface quality (Ra = 0.28 µm, Rz = 1.8 µm) were obtained using a CBN tool. Finally, based on the GRA, the (V = 120 m/min, f = 0.04 mm/rev, a = 0.06 mm, r = 0.8 mm) have been chosen as optimum machining parameters to minimize all responses simultaneously in the machining of AISI 4140 steel using both carbide and CBN inserts. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 5904 KiB

Open AccessArticle

Mechanical Properties and Toughening Mechanisms of Promising Zr-Y-Ta-O Composite Ceramics

by Xiaoteng Fu, Fan Zhang, Wang Zhu and Zhipeng Pi

Coatings 2023, 13(5), 855; https://doi.org/10.3390/coatings13050855 - 30 Apr 2023

Cited by 1 | Viewed by 1402

Abstract

ZrO₂-YO_1.5-TaO_2.5 (ZYTO) composite ceramics are considered to be a candidate for next-generation thermal barrier coatings (TBCs) due to their excellent thermal stability and low thermal conductivity in high temperatures; however, the mechanical properties and fracture toughness of the ZYTO system may be shortcomings compared with 7-8YSZ: the traditional TBC. In this study, ZYTO composite ceramics were successfully prepared by chemical coprecipitation reaction, and the microstructure of resulting composites was studied as a function of the doping of M-YTaO₄. Mechanical properties, including the density, porosity, hardness and Young’s modulus, were all determinate; the toughening mechanism was verified by the crack growth behavior of the Vickers indentation test. The results suggest that M-YTaO₄ refined the fluorite phase grain and strengthened the grain interface in the composite ceramic. The thermal mismatch between the second phase and matrix produced residual stress in the bulk and affected the crack propagation behavior. With the increase in M-YTaO₄ doping, the grain coarsening and ferroelastic domains were observed in the experiments. The ferroelastic domains with orthogonal polarization directions near the crack tip evidenced the ferroelastic toughening mechanism. The competition among these crack behaviors, such as crack deflection, bridging and bifurcation, dominated the actual fracture toughness of the composite. The best toughening formula was determined in the two-phase region, and the highest indentation fracture toughness was about 42 J/m², which was very close to 7-8YSZ’s 45 ± 5 J/m². Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 8096 KiB

Open AccessArticle

Influence of TiC Addition on Corrosion and Tribocorrosion Resistance of Cr₂Ti-NiAl Electrospark Coatings

by Konstantin A. Kuptsov, Mariya N. Antonyuk, Alexander N. Sheveyko, Andrey V. Bondarev and Dmitry V. Shtansky

Coatings 2023, 13(2), 469; https://doi.org/10.3390/coatings13020469 - 18 Feb 2023

Cited by 1 | Viewed by 1905

Abstract

Marine and coastal infrastructures usually suffer from synergetic effect of corrosion and wear known as tribocorrosion, which imposes strict requirements on the structural materials used. To overcome this problem, novel composite wear- and corrosion-resistant xTiC-Fe-CrTiNiAl coatings with different TiC content were successfully developed. The coatings were obtained by the original technology of electrospark deposition in a vacuum using xTiC-Cr₂Ti-NiAl (x = 0, 25, 50, 75%) electrodes. The structure and morphology of the coatings were studied in detail by XRD, SEM, and TEM. The effect of TiC content on the tribocorrosion behavior of the coatings was estimated using tribological and electrochemical (under stationary and wear conditions) experiments, as well as impact testing, in artificial seawater. The TiC-free Fe-Cr₂Ti-NiAl coating revealed a defective inhomogeneous structure with transverse and longitudinal cracks. Introduction of TiC allowed us to obtain coatings with a dense structure without visible defects and with uniformly distributed carbide grains. The TiC-containing coatings were characterized by a hardness and elastic modulus of up to 10.3 and 158 GPa, respectively. Formation of a composite structure with a heavily alloyed corrosion-resistant matrix based on α-(Fe,Cr) solid solution and uniformly distributed TiC grains led to a significant increase in resistance to stationary corrosion and tribocorrosion in artificial seawater. The best 75TiC-Fe-CrTiNiAl coating demonstrated the lowest corrosion current density values both under stationary (0.03 μA/cm²) and friction conditions (0.8 μA/cm²), and was characterized by both a 2-2.5 times lower wear rate (4 × 10⁻⁶ mm³/Nm) compared to AISI 420S steel and 25TiC-Fe-CrTiNiAl and a high fracture toughness. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 6938 KiB

Open AccessFeature PaperArticle

CMAS Corrosion Resistance Behavior and Mechanism of Hf₆Ta₂O₁₇ Ceramic as Potential Material for Thermal Barrier Coatings

by Sai Liu, Qing Liu, Xiaopeng Hu, Jinwei Guo, Wang Zhu, Fan Zhang and Jie Xia

Coatings 2023, 13(2), 404; https://doi.org/10.3390/coatings13020404 - 10 Feb 2023

Cited by 6 | Viewed by 2007

Abstract

Thermal barrier coatings (TBCs) have been seriously threatened by calcium-magnesium-alumina-silicate (CMAS) corrosion. The search for novel ceramic coatings for TBCs with excellent resistance to CMAS corrosion is ongoing. Herein, CMAS corrosion resistance behavior and the mechanism of a promising Hf₆Ta₂O₁₇ ceramic coating for TBCs are investigated. The results show that temperature is the most important factor affecting the CMAS behavior and mechanism. At 1250 °C, the corrosion products are composed of dense reaction products (HfSiO₄, Ca_XHf_6−xTa₂O_17−x) and CMAS self-crystallization products. At 1300 and 1400 °C, the corrosion products are mainly dense CaTa₂O₆ and HfO₂, which prevent further CMAS infiltration. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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12 pages, 3564 KiB

Open AccessArticle

The Influence of H Content on the Properties of a-C(W):H Coatings

by Manuel Evaristo, Filipe Fernandes, Chris Jeynes and Albano Cavaleiro

Coatings 2023, 13(1), 92; https://doi.org/10.3390/coatings13010092 - 3 Jan 2023

Cited by 6 | Viewed by 1868

Abstract

Diamond-like-carbon “DLC” coatings can be deposited in many different ways, giving a large range of material properties suitable for many different types of applications. Hydrogen content significantly influences the mechanical properties and the tribological behavior of DLC coatings, but its determination requires techniques that are not available in many research centers. Thus, it is important to find alternative indirect techniques, such as Raman spectroscopy or nanoindentation (hardness measurements), which can give comparative and indicative values of the H contents in the coatings, particularly when depositions with a reactive gas flow are being studied. In this work, “DLC” composite coatings with varying H content were deposited via Physical Vapor Deposition (PVD) magnetron sputtering in a reactive atmosphere (Ar + CH₄). An Ion Beam Analysis was used to determine the elemental depth profile across the coating thickness (giving both average C:W:H ratios and film density when combined with profilometer measurements of film thickness). The hardness was evaluated with nanoindentation, and a decrease from 16 to 6 GPa (and a decrease in the film density by a factor of two) with an increasing CH₄ flow was observed. Then, the hardness and Raman results were correlated with the H content in the coatings, showing that these indirect methods can be used to find if there are variations in the H content with the increase in the CH₄ flow. Finally, the adhesion and tribological performance of the coatings were evaluated. No significant differences were found in the adhesion as a function of the H content. The tribological properties presented a slight improving trend with the increase in the H content with a decrease in the wear rate and friction. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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14 pages, 2477 KiB

Open AccessArticle

Effect of Standoff Distance on Corrosion Resistance of Cold Sprayed Titanium Coatings

by Mieczyslaw Scendo and Katarzyna Staszewska-Samson

Coatings 2022, 12(12), 1853; https://doi.org/10.3390/coatings12121853 - 30 Nov 2022

Cited by 1 | Viewed by 1711

Abstract

A titanium protective layer was deposited onto Al7075 substrate (Al7075/Ti) by a cold spray method (CS) with different standoff distances (SoD) of the nozzle from the specimen surface. The aim of this research was to study the influence on the mechanical properties and corrosion resistance of the Ti coating on Al7075 substrate. The surface and microstructure of Al7075/Ti was observed by a scanning electron microscope (SEM). The corrosion test of the materials was carried out by using the electrochemical method. The SoD had a significant effect on the microstructure of the coatings and their adhesion onto Al7075 substrate. The highest level of microhardness (248 HV0.3) value was achieved for deposits obtained with the SoD of 70 mm. The corrosion tests showed that the mechanism of electrochemical corrosion of titanium coatings is a multi-stage process, and the main product of the corrosion process was (TiO₂)_ads. However, the polarization resistance (Rp = 49 kΩ cm²) of the Al7075/Ti coatings was the highest, while the corrosion rate (υ_corr = 13.90 mm y⁻¹) was the lowest, for SoD of 70 mm. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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18 pages, 6047 KiB

Open AccessArticle

Quantitative Characterization of Interfacial Defects in Thermal Barrier Coatings by Long Pulse Thermography

by Jinfeng Wei, Guangnan Xu, Guolin Liu, Jinwei Guo, Wang Zhu and Zengsheng Ma

Coatings 2022, 12(12), 1829; https://doi.org/10.3390/coatings12121829 - 26 Nov 2022

Cited by 2 | Viewed by 1358

Abstract

The non-contact long pulse thermography method is commonly used to detect the defects in thermal barrier coatings (TBCs). The profile of interfacial defect in TBCs can be monitored by infrared camera under the irradiation of the excitation source. Unfortunately, the defect profile is always blurry due to heat diffusion between the defect area and the intact area. It is difficult to quantify the size of defect size in TBCs. In this work, combined with derived one-dimensional heat conduction analytical model, a non-contact long pulse thermography (LPT) method is applied to quantitatively investigate the interface defects in TBCs. Principal component analysis (PCA) and background subtraction method are used to improve the contrast of the defect profile in collected thermal images. By fitting the results between the profile of the interface defect in thermal images and the predicted shape of the model, the interface defect size can be determined. Furthermore, a simple extension of proposed method for interfacial defects with irregular shape is presented. The predicted errors for round defect with diameters of 3 mm, 5 mm and 7 mm are roughly distributed in the range of 3%~6%, which are not affected by the defect diameter. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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Review

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21 pages, 702 KiB

Open AccessReview

The Green Lubricant Coatings Deposited by Physical Vapor Deposition for Demanding Tribological Applications: A Review

by Fanlin Kong, Jing Luan, Fuxiang Xie, Zhijie Zhang, Manuel Evaristo and Albano Cavaleiro

Coatings 2024, 14(7), 828; https://doi.org/10.3390/coatings14070828 - 2 Jul 2024

Viewed by 930

Abstract

The emergence of nanotechnology and surface engineering techniques provides new opportunities for designing self-lubricant coatings with enhanced properties. In recent years, green coating technologies have played a vital role in environmental preservation. This article mainly reviews five typical types of self-lubricant coatings including MoN coatings, VN coatings, WN coatings and TMN (Transition Metal Nitride) soft-metal coatings, and DLC (Diamond-like Carbon) with lubricant agents deposited by PVD (Physical Vapor Deposition) for the demanding tribological applications, which is the latest research into the green lubricant coatings. Furthermore, it is of great significance for designing the green self-lubricant coatings to adapt the demanding tribological applications to meet the industrial requirements. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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