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Coatings
Special Issues
Micro- and Nano- Mechanical Testing of Coatings and Surfaces
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Micro- and Nano- Mechanical Testing of Coatings and Surfaces

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

Deadline for manuscript submissions: 31 October 2024 | Viewed by 16205

Special Issue Editors

Prof. Dr. Nigel Jennett

E-Mail Website
Guest Editor
Institute for Future Transport & Cities, Coventry University, Coventry CV1 5FB, UK
Interests: materials; mechanics; length-scale effects; measurement
Special Issues, Collections and Topics in MDPI journals
Dr. Mingwen Bai

E-Mail Website
Guest Editor
School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK
Interests: surface engineering; thermal barrier coatings; thermal spraying coatings; mechanical testing; materials characterization; oxidation and corrosion
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mechanical testing at the micro- and nanoscales has become an integral part of the material science community and is a powerful tool to evaluate materials’ mechanical properties and failure mode/mechanisms. The range of available test methods is increasing in both range of length scales and variety of test conditions, such as high or low temperatures, tribological contact, gas environments, or under radiation exposure. New instrumentation and characterization techniques (e.g., diffraction and imaging) are being used to enhance quantitative characterization of materials by revealing the occurring deformation behavior in real time.

This Special Issue is devoted to capturing recent progress in in situ and ex-situ micro- and nanomechanical testing of inorganic coatings and will focus on quantitative aspects of these techniques as applied to the understanding of coatings’ behavior under varying conditions. Also of interest are the design and development of new in situ test methods and testing in extreme environments.

This issue will cover but not be limited to the following topics:

  • In situ mechanical property testing of coatings (where mechanical tests are performed in an imaging/characterization tool inter alia: synchrotron, electron microscopy, light microscopy, etc.);
  • In situ and operando imaging and microstructural characterization during small-scale testing methods, inter alia: deformation, wear, fatigue, and fracture, etc.;
  • In situ mechanical property testing and operando characterization of coatings in aggressive environments such as high/low temperatures, high strain rate, etc.;
  • Metallic or other inorganic coatings and thin films (thermal/plasma spray, CVD/PVD, etc.);
  • All industrial applications (aerospace, biomedical, electronic, nuclear, etc.);
  • Novel preparation methods and techniques for small-scale testing (FIB, lithography, etc.).

Prof. Dr. Nigel Jennett
Dr. Mingwen Bai
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

  • in situ techniques
  • small-scale mechanical testing
  • coatings and thin films
  • environmental testings
  • failure mechanism

Published Papers (6 papers)

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Research

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10 pages, 3053 KiB  
Article
High-Temperature Tensile Behavior of an As-Cast Ni-W-Co-Ta Medium–Heavy Alloy
by Yong Li, Yi Xiong, Jinjin Tang, Shun Han, Fengzhang Ren, Chunxu Wang and Shubo Wang
Coatings 2024, 14(3), 323; https://doi.org/10.3390/coatings14030323 - 08 Mar 2024
Viewed by 590
Abstract
High-temperature tensile experiments with tensile rates ranging from 0.01 s−1 to 10 s−1 were carried out at various temperatures ranging from 1000 °C to 1250 °C with a Gleeble-3800 thermal simulation tester to evaluate the physical properties of an as-cast Ni–W–Co–Ta [...] Read more.
High-temperature tensile experiments with tensile rates ranging from 0.01 s−1 to 10 s−1 were carried out at various temperatures ranging from 1000 °C to 1250 °C with a Gleeble-3800 thermal simulation tester to evaluate the physical properties of an as-cast Ni–W–Co–Ta medium–heavy alloy. The microstructure evolution of the alloy during high-temperature stretching was characterized by metallographic microscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated the emergence of multiple slip lines and the parallel arrangement of dislocations in the grain of the alloy after high-temperature stretching, and typical characteristics of plane slipping were observed. The plasticity of the Ni–W–Co–Ta medium–heavy alloy increased, but its strength decreased with an increase in the deformation temperature. In contrast, an increase in the strain rate resulted in a noticeable increase in the strength and plasticity of the medium–heavy alloy. The experiments revealed that the maximum tensile strength of the as-cast Ni–W–Co–Ta medium–heavy alloy was 735 MPa (T = 1000 °C, ε˙ = 10 s−1). Additionally, the maximum reduction in area and elongation was 38.1% and 11.8% (T = 1250 °C, ε˙ = 10 s−1), respectively. The mode of fracture after high-temperature tensile deformation was brittle fracturing. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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12 pages, 6661 KiB  
Article
Effect of Aging Time on Microstructure and Properties of Cold-Rolled Ni-W-Co-Ta Medium–Heavy Alloy
by Yong Li, Yi Xiong, Hua-fei Li, Shun Han, Feng-zhang Ren and Chun-xu Wang
Coatings 2024, 14(2), 230; https://doi.org/10.3390/coatings14020230 - 16 Feb 2024
Viewed by 557
Abstract
A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation [...] Read more.
A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation (Ni4W), which persists under various aging times, increases from 13.7% (2 h) to 28.7% (32 h) with the extension of aging time. Meanwhile, the microstructure after aging treatment is still dominated by dislocation entanglement and dislocation walls, although the degree of lattice distortion and dislocation density attributed to heavy deformation decreases. The maximum tensile strength, yield strength, and microhardness (2286 MPa, 1989 MPa, 766 HV) of the cold-rolled Ni-W-Co-Ta medium–heavy alloy under the 16 h aging treatment at 700 °C are reached, respectively. The ductile–brittle mixed fracture morphology is maintained in the fracture morphology of the medium–heavy alloy before and after aging treatment. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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24 pages, 24125 KiB  
Article
Unraveling the Cracking Mechanisms of Air Plasma-Sprayed Thermal Barrier Coatings: An In-Situ SEM Investigation
by Mohamed Amer, Nicholas Curry, Muhammad Arshad, Qamar Hayat, Vit Janik, Jon Nottingham and Mingwen Bai
Coatings 2023, 13(9), 1493; https://doi.org/10.3390/coatings13091493 - 24 Aug 2023
Cited by 1 | Viewed by 1221
Abstract
In this research work, real-time three-point bending coupled with the scanning electron microscopy (SEM) technique were used to study the crack formation and growth of air plasma spraying (APS) thermal barrier coatings (TBCs). The acquired micrographs were then used to study the strain [...] Read more.
In this research work, real-time three-point bending coupled with the scanning electron microscopy (SEM) technique were used to study the crack formation and growth of air plasma spraying (APS) thermal barrier coatings (TBCs). The acquired micrographs were then used to study the strain fields in the vicinity of the cracking region using digital image correlation (DIC) analysis. Fractography analysis for the fractured regions of the APS coatings was also discussed. Based on real-time observation, it was found that roughness of the coatings’ free surface (e.g., valleys) can promote the initiation of cracks since it acts as stress concentration points. Pores and splats features of the coating microstructure contribute to crack branching and crack path deflection, respectively. The former phenomenon (i.e., crack branching) negatively affects the lifetime of the TBC system as it results in an increased fracture area, while the latter can improve the fracture toughness of the coatings and its durability through improving the coating’s ability to dissipate the energy required for crack propagation. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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19 pages, 7579 KiB  
Article
Cracking Behavior of Gd2Zr2O7/YSZ Multi-Layered Thermal Barrier Coatings Deposited by Suspension Plasma Spray
by Mohamed Amer, Nicholas Curry, Qamar Hayat, Rohit Sharma, Vit Janik, Xiang Zhang, Jon Nottingham and Mingwen Bai
Coatings 2023, 13(1), 107; https://doi.org/10.3390/coatings13010107 - 06 Jan 2023
Cited by 5 | Viewed by 4436
Abstract
A new multi-layered thermal barrier coating system (TBCs) containing gadolinium zirconate (GZ, Gd2Zr2O7) and yttria-stabilized zirconia (YSZ) was developed using suspension plasma spray (SPS) to improve the overall thermal cycling performance. This study focuses on the cracking [...] Read more.
A new multi-layered thermal barrier coating system (TBCs) containing gadolinium zirconate (GZ, Gd2Zr2O7) and yttria-stabilized zirconia (YSZ) was developed using suspension plasma spray (SPS) to improve the overall thermal cycling performance. This study focuses on the cracking behavior of the GZ/YSZ TBC after thermal exposure to find out the key factors that limit its lifetime. Different cracking behaviors were detected depending on the thermal treatment condition (i.e., horizontal cracks within the ceramic layer and at the thermally grown oxide (TGO)/YSZ interface) which can be related to stresses developed through thermal expansion mismatch and increased TGO thickness beyond a critical value, respectively. A reduction in hardness of bond coat (BC) was measured by nanoindentation and linked with the thermally activated grain growth mechanism. The hardness and elastic modulus of ceramic layers (GZ and YSZ) showed an increased trend after treatment that contributed to the interfacial cracks. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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13 pages, 7518 KiB  
Article
A Comprehensive Study of Al0.6Ti0.4N Coatings Deposited by Cathodic Arc and HiPIMS PVD Methods in Relation to Their Cutting Performance during the Machining of an Inconel 718 Alloy
by Luca W. Reolon, Myriam H. Aguirre, Kenji Yamamoto, Qinfu Zhao, Igor Zhitomirsky, German Fox-Rabinovich and Stephen Clarence Veldhuis
Coatings 2021, 11(6), 723; https://doi.org/10.3390/coatings11060723 - 16 Jun 2021
Cited by 8 | Viewed by 2531
Abstract
The structural, physical–chemical, and micromechanical characteristics of Al0.6Ti0.4N coatings deposited by different physical vapor deposition (PVD) methods, such as cathodic arc deposition (CAD), as well as advanced HiPIMS techniques were investigated in terms of their cutting performance during the [...] Read more.
The structural, physical–chemical, and micromechanical characteristics of Al0.6Ti0.4N coatings deposited by different physical vapor deposition (PVD) methods, such as cathodic arc deposition (CAD), as well as advanced HiPIMS techniques were investigated in terms of their cutting performance during the machining of an Inconel 718 alloy. XRD studies had revealed that the HiPIMS coating featured lower residual stresses and more fine-grained structure. Electrochemical characterization with the potentiostat-impendence method shows that the HiPIMS coating has a significantly lower porosity than CAD. SEM and AFM studies of the surface morphology demonstrate that the HiPIMS coating has a smoother surface and an absence of droplet phases, in contrast with CAD. XRD, combined with FIB/TEM studies, shows a difference in the crystal structure of both coatings. The micromechanical characteristics of each coating, such as hardness, elastic modulus, fracture toughness, and adhesion to the substrate, were evaluated. The HiPIMS coating was found to possess a more beneficial combination of micromechanical properties compared to CAD. The beneficial characteristics of the HiPIMS coating alleviated the damage of the coated layer under operation. Combined with grain size refinement, this results in the improved adaptive performance of the HiPIMS coating through the formation of a greater amount of thermal barrier sapphire tribo-films on the friction surface. All of these characteristics contribute to the reduction of flank and crater wear intensity, as well as notching, leading to an improvement of the HiPIMS coating’s tool life. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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Review

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34 pages, 80589 KiB  
Review
A Review on In Situ Mechanical Testing of Coatings
by Mohamed Amer, Qamar Hayat, Vit Janik, Nigel Jennett, Jon Nottingham and Mingwen Bai
Coatings 2022, 12(3), 299; https://doi.org/10.3390/coatings12030299 - 23 Feb 2022
Cited by 7 | Viewed by 5454
Abstract
Real-time evaluation of materials’ mechanical response is crucial to further improve the performance of surfaces and coatings because the widely used post-processing evaluation techniques (e.g., fractography analysis) cannot provide deep insight into the deformation and damage mechanisms that occur and changes in coatings’ [...] Read more.
Real-time evaluation of materials’ mechanical response is crucial to further improve the performance of surfaces and coatings because the widely used post-processing evaluation techniques (e.g., fractography analysis) cannot provide deep insight into the deformation and damage mechanisms that occur and changes in coatings’ material corresponding to the dynamic thermomechanical loading conditions. The advanced in situ examination methods offer deep insight into mechanical behavior and material failure with remarkable range and resolution of length scales, microstructure, and loading conditions. This article presents a review on the in situ mechanical testing of coatings under tensile and bending examinations, highlighting the commonly used in situ monitoring techniques in coating testing and challenges related to such techniques. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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