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Coatings
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Compositionally Complex Coatings
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Compositionally Complex Coatings

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

Deadline for manuscript submissions: 30 April 2024 | Viewed by 4268

Special Issue Editors

Dr. Dibakor Boruah

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Guest Editor
Materials Integrity & Performance Technology Group, TWI Ltd., Cambridge CB21 6AL, UK
Interests: coatings; cold spray; thermal spray; structural integrity; residual stresses; materials characterization; machine learning
Dr. Shiladitya Paul

E-Mail Website
Guest Editor
1. Materials Integrity & Performance Technology Group, TWI Ltd., Cambridge CB21 6AL, UK
2. Department of Engineering, University of Leicester, Leicester LE1 7RH, UK
Interests: corrosion; electrochemical monitoring; thermal spray coatings; thermal barrier coatings; carbon capture and storage
Special Issues, Collections and Topics in MDPI journals
Dr. Alvise Bianchin

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Guest Editor
MBN Nanomaterialia, Vascon di Carbonera, Italy
Interests: powder metallurgy; metal composites; mechanical alloying; materials for energy sector
Dr. Francesco Fanicchia

E-Mail Website
Guest Editor
High Temperature Surface Engineering in the Surface Engineering and Precision Centre, School of Aerospace, Transport and Manufacturing (SATM), Cranfield University, Bedford, UK
Interests: coatings; hydrogen economy; aerospace; nuclear fusion; alloy design
Dr. Yuxiang Wu

E-Mail Website
Guest Editor
Department Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
Interests: metallurgy; computational thermodynamics and kinetics; mechanical properties; hydrogen embrittlement; materials degradation; diffraction and microscopy
Dr. Krzysztof Wieczerzak

E-Mail Website
Guest Editor
Laboratory of Mechanics of Materials and Nanostructures, Empa-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
Interests: combinatorial and high-throughput materials science; metallurgical alloy design; steels; hardfacing alloys; complex concentrated alloys; high entropy alloys; thin films
Special Issues, Collections and Topics in MDPI journals
Dr. Alfonso Navarro-López

E-Mail Website
Guest Editor
OCAS NV - Onderzoekscentrum voor de Aanwendig van Staal, Zelzate, Belgium
Interests: high-entropy alloys; compositional complex alloys; coatings; hydrogen barrier; hydrogen embrittlement; wear resistance

Special Issue Information

Dear Colleagues,

The demand for materials to perform well under harsh industrial environments has been pushing materials research forward, not only with incremental improvements in existing conventional materials, but also with the development and discovery of completely new materials.  

In recent years, the concept of ‘multi-principal-elements’ materials has been extensively explored, which involves the mixing of multiple elements without a clear principal element. In the metallurgical community, this leads to a new class of alloys: compositionally complex alloys or complex concentrated alloys (CCAs), which are also termed as high-entropy alloys or medium-entropy alloys. Such a concept is also explored in ceramics, magnetic materials, hard metals, intermetallic compounds, and many functional materials. The large, unexplored compositional space provided by this material strategy enables the design of structural materials exhibiting combined and tailored properties such as excellent tensile strength and ductility, fracture toughness, and wear resistance and corrosion resistance at elevated or cryogenic temperatures.

These materials can find uses as coatings and meet the growing demand for developing cost-effective, highly protective barriers for various applications. This is an interdisciplinary area where material processing, performance and structural/microstructural development are strongly coupled. Now, it is important to communicate within the community regarding these quickly developing compositionally complex coatings (including both alloys, ceramics and composites) to highlight the future directions of the field. This Special Issue plans to give an overview of the most recent advances, emphasising the development of materials as well as deposition techniques, e.g., using thermal spray, cold spray, laser-based, and arc welding techniques for metallic coatings, and slurry-based methods for ceramic coatings, also in addition to sputtering and PVD. Original research articles as well as review papers are welcome. Potential topics include, but are not limited to:

  • Composition design for coating development;
  • Powder manufacturing/ processing;
  • Process parameter optimisation;
  • Microstructure evolution;
  • Mechanical properties (both static and dynamic);
  • Residual stresses;
  • Tribology and corrosion properties;
  • Effect of post-processing, such as thermal treatments;
  • Modelling of alloy development, production process, properties and performance.

Dr. Dibakor Boruah
Dr. Shiladitya Paul
Dr. Alvise Bianchin
Dr. Francesco Fanicchia
Dr. Yuxiang Wu
Dr. Krzysztof Wieczerzak
Dr. Alfonso Navarro-López
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

  • compositionally complex alloys
  • compositionally complex ceramics
  • powder processing
  • coatings
  • repairs
  • cold spray
  • thermal spray
  • laser cladding
  • arc welding
  • wear
  • corrosion
  • microstructure
  • mechanical properties

Published Papers (4 papers)

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Research

14 pages, 3630 KiB  
Article
Machine Learning-Based Predictions of Porosity during Cold Spray Deposition of High Entropy Alloy Coatings
by Deepak Sharma, Dibakor Boruah, Ali Alperen Bakir, Ahamed Ameen and Shiladitya Paul
Coatings 2024, 14(4), 404; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings14040404 - 29 Mar 2024
Viewed by 652
Abstract
Porosity poses a challenge to the mechanical properties of cold sprayed coatings, especially when it is open or surface-connected, limiting the coatings’ capabilities to act as a barrier. The porosity formation is dependent on the feedstock powder characteristics and the cold spray process [...] Read more.
Porosity poses a challenge to the mechanical properties of cold sprayed coatings, especially when it is open or surface-connected, limiting the coatings’ capabilities to act as a barrier. The porosity formation is dependent on the feedstock powder characteristics and the cold spray process parameters. We present a machine learning-based approach to predict porosity based on the above-mentioned factors. Nine different machine learning models based on linear regression (LR), decision trees, random forests, gradient boosting, support vector machine (SVM), and neural networks were explored. Considering the excellent properties of high entropy alloys, Cantor alloy was taken as the consumable. Our dataset, derived from the literature and experiments, identified SVM with a linear kernel and LR as the top-performing models based on the Pearson correlation coefficient (PCC) and root mean square error, where the PCC values exceeded 0.8. The SHapley Additive exPlanations method helped in identifying that the type of gas and powder are the top two factors in pore formation. Full article
(This article belongs to the Special Issue Compositionally Complex Coatings)
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17 pages, 19422 KiB  
Article
Hybrid Ceramic Self-Healing Coatings for Corrosion Protection of Al Alloys in 3% NaCl Solution
by Stefano Mori, Francesca Romana Lamastra and Giampiero Montesperelli
Coatings 2023, 13(10), 1747; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings13101747 - 10 Oct 2023
Cited by 1 | Viewed by 1139
Abstract
This work focuses on the development of sol–gel self-healing coatings for corrosion protection of Al alloys. The use of this method will help to reduce the costs associated with the coating as well as their environmental impact. Coatings were made of a titania [...] Read more.
This work focuses on the development of sol–gel self-healing coatings for corrosion protection of Al alloys. The use of this method will help to reduce the costs associated with the coating as well as their environmental impact. Coatings were made of a titania matrix loaded with microparticles of poly(vinyl-alcohol) (PVA) containing cerium nitrate as an inhibitor. The PVA particles dissolve in water, so that the cerium nitrate deposits on the Al surface subjected to corrosion. The PVA microspheres were made via the emulsion method, and then loaded with cerium nitrate. The amount of cerium nitrate loaded in the microspheres was evaluated using UV–Vis. As a second step, the titania coating with embedded PVA microspheres loaded with cerium nitrate was deposited on an AA6082 substrate via a sol–gel route. The corrosion resistance of the coated samples was tested in NaCl solution. The coating microstructure, before and after the corrosion tests, was analysed with the use of an SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy), while the corrosion resistance was investigated by EIS (electrochemical impedance spectroscopy). The results showed that the coatings were uniform and compact. They also showed the ability of the hybrid TiO2-based coating to provide protection for the AA6082 from corrosion. The coatings with an induced defect (scratch) were also analysed, and the EIS analysis of the coatings over time showed an increase in resistance, confirming the ability of the coating to heal itself. Full article
(This article belongs to the Special Issue Compositionally Complex Coatings)
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22 pages, 4933 KiB  
Article
Preparation and Characterization of Ag2O Thin Films on Construction Textiles for Optoelectronics Applications: Effect of Aging on Its Optical and Structural Properties
by Valentina Krylova, Vaida Dobilaitė and Milda Jucienė
Coatings 2023, 13(9), 1613; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings13091613 - 15 Sep 2023
Viewed by 1001
Abstract
The aim of the research was to modify the surface of construction textiles by means of the use of thin silver oxide films, investigate the structure and optical and mechanical properties, and determine the structure, optical and mechanical properties of the aged composites. [...] Read more.
The aim of the research was to modify the surface of construction textiles by means of the use of thin silver oxide films, investigate the structure and optical and mechanical properties, and determine the structure, optical and mechanical properties of the aged composites. Thin films of silver oxide (Ag2O) were synthesized on a flexible PET/PVC construction textile (CT); the structural, optical, and physical properties, as well as the effect of artificial aging on these properties, were investigated. The SILAR method (successive ionic layer adsorption and reaction) was used to synthesize thin Ag2O films on the CT surface. Before the thin films were deposited, the CT surface was mechanically roughened and pretreated with acidic and alkaline solutions at an elevated temperature. XRD analysis showed that the deposited films were a polycrystalline mixed phase material consisting of Ag2O, AgO, and metallic Ag. Diffuse reflectance spectra in the ultraviolet and visible ranges (UV-Vis) were used to study the optical properties of the deposited thin films. The synthesized Ag2O/CT composites were direct-gap semiconductors (the optical band gap (Eg) was 0.89 ± 0.02 eV). Eg and refractive indices (n) increased as the aging tests were carried out. Higher Eg and n meant that the composites were a good material for optoelectronic applications. The results showed that, after modification, the structural properties and tear strength of the PET/PVC fabric remained the same while the tensile strength decreased. The same tendencies remained after artificial aging. Full article
(This article belongs to the Special Issue Compositionally Complex Coatings)
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15 pages, 14035 KiB  
Article
Machine Hammer Peening and Its Effect on the Surface Integrity of Arc-Sprayed WC-W2C-FeCMnSi Coatings
by Leif Hagen, Jonas Baumann, Markus Heidelmann, Dirk Biermann and Wolfgang Tillmann
Coatings 2023, 13(9), 1563; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings13091563 - 06 Sep 2023
Cited by 1 | Viewed by 853
Abstract
With respect to post-processing techniques in the field of surface engineering, it was recently found that machine hammer peening (MHP) represents a promising approach to functionalizing thermally sprayed coatings as the MHP contributes to a compression of the coating, enabling the potential to [...] Read more.
With respect to post-processing techniques in the field of surface engineering, it was recently found that machine hammer peening (MHP) represents a promising approach to functionalizing thermally sprayed coatings as the MHP contributes to a compression of the coating, enabling the potential to reduce the coating porosity as well as the protruding peaks of the rough as-sprayed coating surface. The MHP also has the potential to induce compressive residual stresses in the coating surface, which can positively affect the mechanical and tribological properties. Arc-sprayed tungsten carbide-reinforced Fe-based coatings pose an appropriate candidate to counteract the wear of tribologically stressed surfaces. Due to the inherent process characteristics, however, these coatings are mostly characterized by a heterogeneous lamellar microstructure with residual porosity and interstratified with a certain amount of oxides, as well as the presence of tensile residual stresses. To adjust their microstructural and mechanical coating properties, the applicability of a subsequent MHP was evaluated in this study. Therefore, arc-sprayed WC-W2C reinforced FeCMnSi coatings are deposited using either argon or compressed air as atomization and shroud gas, providing different lamellar structures and oxide content. The effect of MHP on the surface integrity of the WC-W2C-FeCMnSi coating is investigated with respect to its porosity, lamellar structure, hardness, and residual stresses, which are known as relevant influencing factors on the performance of tribologically stressed components. It was found that the MHP leads to reduced porosity and lamella thickness as well as increased hardness due to strain hardening effects. Furthermore, it was demonstrated that the MHP leads to the introduction of compressive residual stresses, which contribute to a decline in tensile residual stresses in the near-surface area. Full article
(This article belongs to the Special Issue Compositionally Complex Coatings)
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