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Surface Modification and Functionalization of High-Temperature Alloys

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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 (15 May 2021) | Viewed by 19301

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Special Issue Editor

Dr. Joon Sik Park

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Guest Editor

Department of Material Sciences and Engineering, Hanbat National University, Daejeon 34158, Republic of Korea
Interests: coatings; high temperature; composites; interface; oxidation; diffusion

Special Issue Information

Dear Colleagues,

I would like to invite you to submit your work to this Special Issue on the topic of "Surface Modification and Functionalization of High-Temperature Alloys". Surface coatings are often an effective route for enhancing materials inherit properties. In particular, when structural compartments are exposed to high-temperature environments under an ambient atmosphere, surface protection is needed for the substrate, such as Mo- and/or Nb-based alloys, Ni-based alloys, Ti-based alloys, high entropy alloys or composites, and so on. Often the alloys are exposed to a high-temperature flame for a long or short time. In this regard, studies for advanced and compatible coatings are critical for the successful development of practical applications. In order to fulfil the task, theoretical and experimental efforts are needed for achieving repetitive and reliable properties. This Special Issue of Coatings focuses on the aforementioned areas. Our aim is to present the recent developments in this fast-moving field around the world.

Dr. Joon Sik Park
Guest Editor

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 modification of structural materials for improving high-temperature performance
Ceramic coatings for high-temperature applications
Improvement of surface protection via in-situ coatings
External surface treatment for improving oxidation resistance
Plasma treatments to improve the performance of coatings at high temperatures
Functionalization of coatings for achieving compatible coating layer design
Analytical and computational models for understanding coatings
Practical coating approaches for enhancing materials properties at high temperatures

Published Papers (6 papers)

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Research

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14 pages, 4145 KiB

Open AccessArticle

Interfacial Structure and Physical Properties of High-Entropy Oxide Coatings Prepared via Atmospheric Plasma Spraying

by Tae-sung Park, Nana Kwabena Adomako, Andrews-nsiah Ashong, Young-kuk Kim, Seung-min Yang and Jeoung-han Kim

Coatings 2021, 11(7), 755; https://doi.org/10.3390/coatings11070755 - 24 Jun 2021

Cited by 7 | Viewed by 2336

Abstract

The feasibility of using a high-entropy rare-earth oxide (REO) as a top coating material for thermal barrier coatings was explored using the atmospheric plasma spray technique. The microstructure and Vickers hardness of the coating layer were compared to those of an 8 mol % yttria-stabilized zirconia (8YSZ) top coating material. Macroscopic observations revealed the formation of a well-coated surface with no surface defects or delamination. Scanning electron microscopy images showed the presence of several parallel and vertical microcracks in the REO and 8YSZ coating layers. The origin of these cracks is attributed to differences in the coefficient of thermal expansion, very fast cooling, and process parameters. X-ray diffraction demonstrated the high phase stability and excellent thermal properties of REO due to the absence of phase transformation after plasma spray processing. The measured Vickers hardness of REO was 425 HV, which is lower than that of sintered REO powder and the 8YSZ coating. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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8 pages, 3112 KiB

Open AccessArticle

Microstructure and Oxidation Resistance of Cr–Al–Si Alloys for High-Temperature Applications

by Jeong-Min Kim and Chae-Young Kim

Coatings 2020, 10(4), 329; https://doi.org/10.3390/coatings10040329 - 30 Mar 2020

Cited by 2 | Viewed by 2437

Abstract

Cr–Al alloys are attracting much attention as heat- and corrosion-resistant coating materials due to their excellent high-temperature properties. In order to investigate the effect of aluminum content on the microstructure and oxidation resistance of Cr–Al–Si alloys, cast specimens were prepared by using a vacuum-arc melting furnace, and high-temperature oxidation tests were conducted with the specimens, for 1 h, at 1100 °C, in air. In the case of cast microstructure of Cr–Al–Si alloys, it consists mainly of Cr single phase, up to 5 at.% Al, and AlCr phases were additionally formed in alloys containing 10% Al or more. In the specimen with 20% Al added, CrSi phase was also found in addition to the AlCr phase. The weight change of the specimens heated for 1 h, at 1100 °C, indicated that all had excellent oxidation resistance. However, when the Al content was less than 10%, the weight gain tended to be a little lower than that of 10% or more. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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11 pages, 2236 KiB

Open AccessArticle

Influence of N₂ Gas Flow Ratio and Working Pressure on Amorphous Mo–Si–N Coating during Magnetron Sputtering

by Ki Seong Lim, Young Seok Kim, Sung Hwan Hong, Gian Song and Ki Buem Kim

Coatings 2020, 10(1), 34; https://doi.org/10.3390/coatings10010034 - 01 Jan 2020

Cited by 7 | Viewed by 2944

Abstract

In this study, Mo–Si–N coatings were deposited on Si wafers and tungsten carbide substrates using a reactive direct current magnetron sputtering system with a MoSi powder target. The influence of sputtering parameters, such as the N₂ gas flow ratio and working pressure, on the microstructure and mechanical properties (hardness (H), elastic modulus (E), and H/E ratio) of the Mo–Si–N coatings was systematically investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), nanoindentation, and transmission electron microscopy (TEM). The gas flow rate was a significant parameter for determining the crystallinity and microstructure of the coatings. A Mo₂N crystalline coating could be obtained by a high N₂ gas flow ratio of more than 35% in the gas mixture, whereas an amorphous coating could be formed by a low N₂ gas flow ratio of less than 25%. Furthermore, the working pressure played an important role in controlling the smooth surface and densified structure of the Mo–Si–N coating. For the amorphous Mo–Si–N coating deposited with the lowest working pressure (1 mTorr), the hardness, elastic modulus, and H/E ratio reached from 9.9 GPa, 158.8 GPa, and 0.062 up to 17.9 GPa, 216.1 GPa, and 0.083, respectively. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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12 pages, 2027 KiB

Open AccessArticle

Structural and Mechanical Properties of AlCoCrNi High Entropy Nitride Films: Influence of Process Pressure

by Young Seok Kim, Hae Jin Park, Ki Seong Lim, Sung Hwan Hong and Ki Buem Kim

Coatings 2020, 10(1), 10; https://doi.org/10.3390/coatings10010010 - 21 Dec 2019

Cited by 20 | Viewed by 3987

Abstract

In the present study, novel AlCoCrNi high entropy nitride (HEN) films were deposited on Si substrate by a reactive direct current magnetron sputtering system. In order to investigate the influence of sputtering parameters on the microstructure and mechanical properties of the film, nitrogen flow ratio (R_N: 25–100%) and process pressure (1.33 × 10⁻¹–1.33 Pa) were controlled, respectively. All the films were identified as an amorphous phase with composition of near equiatomic ratios, regardless of the conditions of nitrogen flow ratios and process pressures. However, the limited mechanical properties were found for the films deposited under different nitrogen flow ratios with retaining the process pressure of 1.33 Pa. To enhance the mechanical properties of the AlCoCrNi HEN film, process pressure was adjusted. From the transmission electron microscopy (TEM) observation, the structure of the film deposited at the process pressure of 1.33 Pa is identified as a porous and open structure with a number of density-deficient boundary and nano-scale voids. On the other hand, densified morphology of the film was observed at pressure of 1.33 × 10⁻¹ Pa. As a result, the hardness, elastic modulus, and H/E were improved up to 16.8, 243 GPa, and 0.0692, respectively. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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13 pages, 5173 KiB

Open AccessFeature PaperArticle

Microstructures and Oxidation Behavior According to Nb:Mo Ratio in a Nb–Mo–Si System with Si Pack Cementation Coatings

by Wonchul Yang, Choong-Heui Chung, Sangyeob Lee, Jong Won Lee and Joon Sik Park

Coatings 2019, 9(12), 772; https://doi.org/10.3390/coatings9120772 - 20 Nov 2019

Cited by 2 | Viewed by 2387

Abstract

Research is being conducted on Mo- and Nb-based alloys that are used in the aerospace sector, including those used for advanced gas turbines and aircraft engines. There is a limit to using Mo, which has a high density among refractory metals, and a few studies exist describing the addition of Nb to Mo–silicide alloys. There is a lack of guidance research on the basic Nb:Mo ratio of alloys, and it is necessary to study how to improve oxidation resistance. Therefore, this study aims to improve oxidation resistance by controlling the ratio of Nb and Mo in (Nb_x, Mo_y)Si₂ coating layers with Si pack cementation coatings on Nb–Mo alloys. Static oxidation tests were carried out at 1200 °C for 6 h to confirm the oxidation characteristics. As a result, a SiO₂ or SiO₂ + Nb₂O₅ ceramic protective layer was formed on the surface. After the oxidation tests, alloys with a Nb content of less than 35 at.% were found to protect the surface. The ratios of Nb and Mo in the Nb–Mo alloy and silicide coating layer were compared, and the improvement of oxidation resistance is discussed in terms of microstructural evolution. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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Review

Jump to: Research

18 pages, 5566 KiB

Open AccessReview

Corrosion Behavior and Surface Treatment of Cladding Materials Used in High-Temperature Lead-Bismuth Eutectic Alloy: A Review

by Hao Wang, Jun Xiao, Hui Wang, Yong Chen, Xing Yin and Ning Guo

Coatings 2021, 11(3), 364; https://doi.org/10.3390/coatings11030364 - 23 Mar 2021

Cited by 33 | Viewed by 4629

Abstract

Liquid metal fast reactors were considered to be the most promising solution to meet the enormous energy demand in the future. However, corrosion phenomenon caused by the liquid metal, especially in high-temperature lead-bismuth coolant, has greatly hindered the commercialization of the advanced Generation-IV nuclear system. This review discussed current research on the corrosion resistance of structural materials (such as EP823, T91, ODS, and authentic steels) in high-temperature liquid metal served as reactor coolants. The current corrosion resistance evaluation has proved that even for the excellent performance of EP823, the structural material selected in pressurized water reactor is not the ideal material for operation in the high-temperature lead-bismuth eutectic (LBE). Furthermore, the latest coating technologies that are expected to be applied to cladding materials for coolant system were extensively discussed, including Al-containing coatings, ceramic coatings, oxide coatings, amorphous coatings and high-entropy alloy coatings. The detailed comparison summarized the corrosion morphology and corrosion products of various coatings in LBE. This review not only provided a systematic understanding of the corrosion phenomena, but also demonstrated that coating technology is an effective method to solve the corrosion issues of the advanced next-generation reactors. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization of High-Temperature Alloys)

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