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Special Issue "Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II)"

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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: 30 November 2023 | Viewed by 4515

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Special Issue Editors

Prof. Dr. Francesca Borgioli

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Guest Editor

Department of Industrial Engineering (DIEF), Università di Firenze, via di S. Marta 3, 50139 Firenze, Italy
Interests: surface modification of metals and alloys; low-temperature nitriding of stainless steels; oxynitriding of titanium alloys; material characterization
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Dr. Shinichiro Adachi

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Guest Editor

Osaka Research Institute of Industrial Science and Technology, Osaka, Japan
Interests: plasma nitriding; plasma carburizing; thermal spraying; laser metal deposition
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Dr. Thomas Lindner

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Guest Editor

Materials and Surface Engineering Group, Institute of Materials Science and Engineering, Chemnitz University of Technology, 09107 Chemnitz, Germany
Interests: thermal spraying; thermochemical treatment; heat treatment; Spark Plasma Sintering; laser cladding; high-entropy alloys; stainless-steel; Wear; corrosion; Microstructure
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The formation of an expanded austenite phase (S-phase) by low-temperature thermochemical treatments using nitrogen and/or carbon (nitriding, carburizing and nitrocarburizing) of stainless steels has been studied since the 1980s. Initially, this method was applied to austenitic stainless steels, but it has proved to be suitable to produce expanded phases not only on the different grades of stainless steels (duplex, martensitic, precipitation-hardening and ferritic), but also on cobalt- and nickel-based alloys, and, recently, on high entropy alloys. The discovery of important scientific findings and their practical applications in industry have been achieved. In recent years, it has been combined with new processes such as thermal spray coating and additive manufacturing techniques, and it is expected to contribute to the manufacturing of the next generation.

This Special Issue on “Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties” intends to cover original research and critical review articles on recent advances in all aspects of low-temperature thermochemical treatments using nitrogen and/or carbon.

In particular, the topics of interest include, but are not limited to, the following:

Fundamentals and new concepts;
Characteristics and properties of the expanded phases;
Characteristics and properties of the modified layers;
Application to novel alloys;
Combination with other manufacturing processes;
Industrial applications.

Prof. Dr. Francesca Borgioli
Dr. Shinichiro Adachi
Dr. Thomas Lindner
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. Metals 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

low-temperature nitriding
low-temperature carburizing
low-temperature nitrocarburizing
expanded austenite (S-phase)
expanded phases
material properties
material characterization

Published Papers (5 papers)

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Research

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15 pages, 11066 KiB

Open AccessArticle

Identification of Expanded Austenite in Nitrogen-Implanted Ferritic Steel through In Situ Synchrotron X-ray Diffraction Analyses

Bruna C. E. Schibicheski Kurelo

Carlos M. Lepienski

Willian R. de Oliveira

Gelson B. de Souza

Francisco C. Serbena

Rodrigo P. Cardoso

Julio C. K. das Neves

and

Paulo C. Borges

Metals 2023, 13(10), 1744; https://doi.org/10.3390/met13101744 - 14 Oct 2023

Viewed by 590

Abstract

The existence and formation of expanded austenite in ferritic stainless steels remains a subject of debate. This research article aims to provide comprehensive insights into the formation and decomposition of expanded austenite through in situ structure analyses during thermal treatments of ferritic steels. To achieve this objective, we employed the Plasma Immersion Ion Implantation (PIII) technique for nitriding in conjunction with in situ synchrotron X-ray diffraction (ISS-XRD) for microstructural analyses during the thermal treatment of the samples. The PIII was carried out at a low temperature (300–400 °C) to promote the formation of metastable phases. The ISS-XRD analyses were carried out at 450 °C, which is in the working temperature range of the ferritic steel UNS S44400, which has applications, for instance, in the coating of petroleum distillation towers. Nitrogen-expanded ferrite (α_N) and nitrogen-expanded austenite (γ_N) metastable phases were formed by nitriding in the modified layers. The production of the α_N or γ_N phase in a ferritic matrix during nitriding has a direct relationship with the nitrogen concentration attained on the treated surfaces, which depends on the ion fluence imposed during the PIII treatment. During the thermal evolution of crystallographic phase analyses by ISS-XRD, after nitriding, structure evolution occurs mainly by nitrogen diffusion. In the nitrided samples prepared under the highest ion fluences—longer treatment times and frequencies (PIII 300 °C 6 h and PIII 400 °C 3 h) containing a significant amount of γ_N—a transition from the γ_N phase to the α and CrN phases and the formation of oxides occurred. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))

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19 pages, 13061 KiB

Open AccessArticle

Assessment of the Pitting, Crevice Corrosion, and Mechanical Properties of Low-Temperature Plasma-Nitrided Inconel Alloy 718

Yamid Nuñez de la Rosa

Oriana Palma Calabokis

Vladimir Ballesteros-Ballesteros

Cristian Lozano Tafur

and

Paulo C. Borges

Metals 2023, 13(7), 1172; https://doi.org/10.3390/met13071172 - 23 Jun 2023

Cited by 1 | Viewed by 643

Abstract

A comparative study on the mechanical properties, scratch resistance, and localized corrosion (pitting and crevice) of plasma-nitrided Inconel alloy 718 (UNS NO7718: IN 718) was carried out. Thermochemical treatment was performed at low temperatures (400 and 450 °C) for 4 h. The treatment formed layers with thicknesses of 7.17 ± 0.89 µm (400 °C) and 7.96 ± 0.48 µm (450 °C). The XRD and nanohardness analyses indicated the formation of a hard layer composed of the expanded austenite phase (γ_N), CrN at 400 °C, and CrN + γ at 450 °C, with a maximum indentation hardness of 12 and 12.5 GPa, respectively, when compared to the 5 GPa substrate hardness. The scratching tests (2–8 N) showed that with increasing load, the nitrided surfaces had a transition from 100% microcutting to a combination of microplowing/cutting, with the presence of cracks. The critical load of the nitrided surfaces was 3 N for 400 °C and 4 N for 450 °C. The untreated condition maintained a crack-free combined mechanism regardless of the load. For the same load, the nitrided surfaces held lower coefficient of friction values and higher scratch resistance values, which were more pronounced at 450 °C. The linear polarization tests (3.56 wt.% NaCl) showed pitting corrosion in all samples, with the 450 °C condition being less resistant. Nitriding at 400 °C increased the crevice corrosion resistance of Inconel, while at 450 °C, it severely damaged it. Nitriding at 400 °C brought concomitant gains in hardness and scratch and crevice corrosion resistance when compared to the as-received IN 718. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))

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15 pages, 5449 KiB

Open AccessArticle

Electrochemical Corrosion Behavior of Ti-N-O Modified Layer on the TC4 Titanium Alloy Prepared by Hollow Cathodic Plasma Source Oxynitriding

and

Metals 2023, 13(6), 1083; https://doi.org/10.3390/met13061083 - 07 Jun 2023

Cited by 1 | Viewed by 647

Abstract

TC4 alloy is widely used in dental implantation due to its excellent biocompatibility and low density. However, it is necessary to further improve the corrosion resistance and surface hardness of the titanium alloy to prevent surface damage that could result in the release of metal ions into the oral cavity, potentially affecting oral health. In this study, Ti-N-O layers were fabricated on the surface of TC4 alloy using a two-step hollow cathode plasma source oxynitriding technique. This resulted in the formation of TiN, Ti₂N, TiO₂, and nitrogen-stabilized α(N)-Ti phases on the TC4 alloy, forming a Ti-N-O modified layer. The microhardness of the samples treated with plasma oxynitriding (PNO) was found to be 300–400% higher than that of untreated (UN) samples. The experimental conditions were set at 520 °C, and the corrosion current density of the PNO sample was measured to be 7.65 × 10⁻⁸ A/cm², which is two orders of magnitude lower than that of the UN sample. This indicates that the PNO-treated TC4 alloy exhibited significantly improved corrosion resistance in the artificial saliva solutions. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))

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12 pages, 11627 KiB

Open AccessArticle

Mechanical and Magnetic Investigations of Balls Made of AISI 1010 and AISI 1085 Steels after Nitriding and Annealing

Sławomir Maksymilian Kaczmarek

and

Metals 2023, 13(6), 1060; https://doi.org/10.3390/met13061060 - 01 Jun 2023

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Abstract

This paper discusses the changes in the phase composition and magnetic properties of the AISI 1010 and AISI 1085 steels that were nitrided at 570 °C in an ammonia atmosphere for 5 h and that were then annealed at 520 °C in a N₂/Ar atmosphere for 4 h. The test samples were made in the form of balls with diameters of less than 5 mm. The thickness of the obtained iron nitride layers was assessed through metallographic tests, while the phase composition was verified through X-ray tests. The magnetic properties were determined using ferromagnetic resonance (FMR) and superconducting quantum interference device (SQUID) techniques. Our research shows that, during the annealing of iron nitrides with a structure of ε + γ′, the ε phase decomposes first. As a result of this process, an increase in the content of the γ′ phase of the iron nitride is observed. When the ε phase is completely decomposed, the γ′ phase begins to decompose. The observed FMR signals did not come from isolated ions but from more magnetically complex systems, e.g., Fe–Fe pairs or iron clusters. Studies have shown that nitriding and annealing can be used to modify the magnetic properties of the tested steels. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))

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Review

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33 pages, 9358 KiB

Open AccessReview

The Corrosion Behavior in Different Environments of Austenitic Stainless Steels Subjected to Thermochemical Surface Treatments at Low Temperatures: An Overview

Francesca Borgioli

Metals 2023, 13(4), 776; https://doi.org/10.3390/met13040776 - 15 Apr 2023

Cited by 7 | Viewed by 1418

Abstract

Low-temperature thermochemical treatments are particularly suitable for use in the surface hardening of austenitic stainless steels without impairing their corrosion resistance. In fact, when using treatment media rich in nitrogen and/or carbon at relatively low temperatures (<450 °C for nitriding, <550 °C for carburizing), it is possible to inhibit the formation of chromium compounds and obtain modified surface layers that consist mainly of a supersaturated solid solution, known as expanded austenite or S-phase. It has been observed that this hard phase allows the enhancement of corrosion resistance in chloride-ion-containing solutions, while the results were contradictory for chloride-free acidic solutions. This overview aims to discuss the corrosion behavior of low-temperature-treated austenitic stainless steels, taking into account the different microstructures and phase compositions of the modified layers, as well as the different test environments and conditions. In particular, the corrosion behavior in both chloride-ion-containing solutions and chloride-free solutions (sulfuric acid, sulfate and borate solutions) is discussed. The analysis of the international literature presents evidence that the microstructure and phase composition of the modified layers have key roles in corrosion resistance, especially in sulfuric acid solutions. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))

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