Research

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9 pages, 10770 KiB

Open AccessCommunication

A Study of the Hot Salt Corrosion Behavior of Three Nickel-Based Single-Crystal Superalloys at 900 °C

by Qianyi Li, Feng Liu, Yixin Li, Jian Yao, Jingyu Yang, Liming Tan, Zi Wang, Lan Huang and Yong Liu

Crystals 2024, 14(4), 307; https://doi.org/10.3390/cryst14040307 - 27 Mar 2024

Viewed by 501

Abstract

A study of the hot salt corrosion behavior of three nickel-based single-crystal superalloys at 900 °C was conducted. We discovered that the corrosion layer on each alloy was distinctly enriched with Mo, Ni, S, and O, primarily comprising sulfides and oxides. Notably, variations [...] Read more.

A study of the hot salt corrosion behavior of three nickel-based single-crystal superalloys at 900 °C was conducted. We discovered that the corrosion layer on each alloy was distinctly enriched with Mo, Ni, S, and O, primarily comprising sulfides and oxides. Notably, variations in oxygen distribution across the alloys revealed that the elemental composition plays a pivotal role in their corrosion resistance. These insights not only advance our understanding of the mechanisms driving thermal corrosion in nickel-based single-crystal superalloys but also lay the groundwork for designing alloys with enhanced durability tailored to high-temperature applications. This research marks a significant step toward the optimal design and utilization of superalloys in sectors demanding exceptional material stability under thermal stress. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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22 pages, 6493 KiB

Open AccessArticle

Atomic-Level Description of Chemical, Topological, and Surface Morphology Aspects of Oxide Film Grown on Polycrystalline Aluminum during Thermal Oxidation—Reactive Molecular Dynamics Simulations

by Marcela E. Trybula, Arkadiusz Żydek, Pavel A. Korzhvayi and Joanna Wojewoda-Budka

Crystals 2023, 13(9), 1376; https://doi.org/10.3390/cryst13091376 - 14 Sep 2023

Viewed by 609

Abstract

Oxidation results in the formation of an oxide film whose properties and structure can be tailored by controlling the oxidation conditions. Reactive molecular dynamics simulations were performed to study thermal oxidation of polycrystalline Al substrates as a function of O₂ density and [...] Read more.

Oxidation results in the formation of an oxide film whose properties and structure can be tailored by controlling the oxidation conditions. Reactive molecular dynamics simulations were performed to study thermal oxidation of polycrystalline Al substrates as a function of O₂ density and temperature. The structural, chemical, and topological aspects of polycrystalline Al (poly-Al) substrates and oxide films formed upon oxidation were studied. The studies were supported by surface topography and morphology analyses before and after oxidation. An analysis of Al–O atomic pair distribution showed the development of long-range order in the oxide films grown upon exposure to low-density (0.005 g/cm³) and high-density (0.05 g/cm³) O₂ gas. The long-range order was more apparent for the high-density environment, as the oxide films formed in low-density O₂ gas did not fully cover the poly-Al surface. The dominance of over-coordinated polyhedral units in a tightly packed structure was indicative of medium- and long-range atomic order in the oxide films. The two-phase structure of the oxide was found in the films, with a crystalline phase at the metal/oxide interface and an amorphous phase at the oxide/O₂ interface. The combination with topological analyses supported the conclusions of the chemical analysis and enabled us to capture an amorphous-to-crystalline phase transformation in the oxide films with increasing oxygen density and temperature. An important effect of Al surface roughness before oxidation on the behavior of the metal/oxide interface and on the oxide film structure was observed. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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19 pages, 5560 KiB

Open AccessArticle

Experimental Study of the Evolution of Creep-Resistant Steel’s High-Temperature Oxidation Behavior

by Gabriela Baranová, Mária Hagarová, Miloš Matvija, Dávid Csík, Vladimír Girman, Jozef Bednarčík and Pavel Bekeč

Crystals 2023, 13(6), 982; https://doi.org/10.3390/cryst13060982 - 20 Jun 2023

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Abstract

This study shows that in an atmosphere containing water vapor, the oxide layer on the surface of the 9CrNB steel MarBN (Martensitic 9Cr steel strengthened by Boron and MX Nitrides) was formed by an outer layer of hematite Fe₂O₃ and [...] Read more.

This study shows that in an atmosphere containing water vapor, the oxide layer on the surface of the 9CrNB steel MarBN (Martensitic 9Cr steel strengthened by Boron and MX Nitrides) was formed by an outer layer of hematite Fe₂O₃ and Cr₂O₃ and an inner two-phase layer of Fe₃O₄ and Fe₃O₄ + (Fe, Cr)₂O₄, which was confirmed by XRD analysis. Part of the layer consisted of nodules and pores that were formed during the increase in oxides when the present H₂O(g) acted on the steel surface. The diffusion mechanism at temperatures of 600 and 650 °C and at longer oxidation times supported the “healing process” with a growing layer of Fe oxides and the presence of Cr and minor alloying elements. The effects of alloying elements were quantified using a concentration profile of the oxide layer based on quantitative SEM analysis, as well as an explanation of the mechanism influencing the structure and chemical composition of the oxide layer and the steel-matrix–oxide interface. In addition to Cr, for which the content reached the requirement of exceeding 7.0 wt. % in the inner oxide layer, W, Co, Mn, and Si were also found in increased concentrations, whether in the form of the present Fe-Cr spinel oxide or as part of a continuously distributed layer of Mn₂O₃ and SiO₂ oxides at the steel-matrix–oxide interface. After long-term high-temperature oxidation, coarser carbides of the M₂₃C₆ type (M = Fe,W) significantly depleted in Cr were formed at the oxide-layer/matrix interface. In the zone under the oxide layer, very fine particles of MC (M = V, Nb, and to a lesser extent also Cr in the particle lattice of the given phase) were observed, with a higher number of particles per unit area compared to the state before oxidation. This fact was a consequence of Cr diffusion to the steel surface through the subsurface zone. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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19 pages, 5904 KiB

Open AccessArticle

Influence of Silicon and Chromium on the Na₂SO₄-Induced Hot Corrosion Behavior of Titanium Alloys

by Marzena Mitoraj-Królikowska

Crystals 2023, 13(6), 948; https://doi.org/10.3390/cryst13060948 - 12 Jun 2023

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Abstract

Titanium alloys are widely used as construction materials in the aerospace and automotive industries. They have many advantages but also have limitations related to their susceptibility to high-temperature oxidation and hot corrosion. Many efforts to increase the lifetime of components made of titanium [...] Read more.

Titanium alloys are widely used as construction materials in the aerospace and automotive industries. They have many advantages but also have limitations related to their susceptibility to high-temperature oxidation and hot corrosion. Many efforts to increase the lifetime of components made of titanium alloys have been reported in the literature; the most promising ones involve the deposition of coatings. The present paper is focused on the development of coatings containing chromium and silicon, and their further evaluation in hot corrosion tests. It was proved that the Cr-Si coatings were more effective than Si coatings alone in protecting the titanium alloys against Na₂SO₄-induced hot corrosion at 800 °C. The enhanced corrosion resistance was attributed to the preferential formation of a thick and continuous SiO₂ layer on the surface and—in the case of titanium aluminide alloy—the growth of an Al₂O₃-rich inner layer of the scale, promoted by chromium. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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16 pages, 23446 KiB

Open AccessArticle

Processing, Characterization, and Oxidation Resistance of Glass-Ceramic Coating on CoSb₃

by Kinga M. Zawadzka, Fabiana D’Isanto, Krzysztof Mars, Federico Smeacetto and Milena Salvo

Crystals 2023, 13(6), 880; https://doi.org/10.3390/cryst13060880 - 27 May 2023

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Abstract

Power generation based on thermoelectric (TE) materials is very attractive due to its low environmental impact and waste heat recovery. Thermoelectric materials based on cobalt triantimonide CoSb₃ exhibit one of the highest energy conversion efficiencies, revealing thermoelectric figures of merit, ZTs > [...] Read more.

Power generation based on thermoelectric (TE) materials is very attractive due to its low environmental impact and waste heat recovery. Thermoelectric materials based on cobalt triantimonide CoSb₃ exhibit one of the highest energy conversion efficiencies, revealing thermoelectric figures of merit, ZTs > 1, but undergo oxidation above 380 °C and sublimation above 500 °C. In this work, a glass-ceramic coating was chosen to match the coefficient of thermal expansion (CTE) of the TE substrate 9.2 × 10⁻⁶ K⁻¹ (200–400 °C), deposition temperature (max. 700 °C), and maximum working temperature (600 °C). Coating processing involved the production of glass powder and glass-ceramic sintering. The glass-ceramic and the coating/CoSb₃ interface were systematically investigated by means of dilatometry, X-ray diffraction, and scanning and transmission electron microscopy. As a result, a coating with good substrate coverage and adherence was developed. Finally, oxidation tests were carried out at 500 and 600 °C in order to assess the protective properties of the glass-ceramic. Microstructural and chemical composition analysis indicated limited protective properties of the coating. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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19 pages, 11182 KiB

Open AccessArticle

Oxidation and Electrical Property Studies on Ferritic Steels as Potential Interconnects in Electrochemical Devices for Energy Conversion

by Jarosław Dąbek, Richard Gaweł, Michał Pyzalski and Tomasz Brylewski

Crystals 2023, 13(6), 862; https://doi.org/10.3390/cryst13060862 - 24 May 2023

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Abstract

This work presents the results of oxidation studies on commercially available Nirosta 4016/1.4016 ferritic steel, which contains 16.3 wt.% chromium, as well as the electrical properties of steel/scale layer systems in order to determine the usefulness of this steel for constructing metallic interconnects [...] Read more.

This work presents the results of oxidation studies on commercially available Nirosta 4016/1.4016 ferritic steel, which contains 16.3 wt.% chromium, as well as the electrical properties of steel/scale layer systems in order to determine the usefulness of this steel for constructing metallic interconnects in solid oxide fuel cell (SOFC) and solid oxide electrolyzer cell (SOEC) stacks. The E-Brite ferritic steel, consisting of up to 26 wt.% chromium, was chosen as a reference material. High-temperature isothermal oxidation kinetics studies were carried out on both steels at 1073 K for 255, 505, 760 and 1010 h in air atmosphere. These conditions are representative of those present in the cathode compartment of a SOFC and the anode compartment of a SOEC. Area specific resistance (ASR) measurements were performed on steel/scale layer systems, obtained after the previous oxidation of both steels in the above-mentioned conditions, in the air in the temperature range of 573–1073 K using the pseudo-DC four-probe method. On the basis of these studies, complemented by morphology observations, as well as chemical and phase composition analysis of the oxidation products, the usefulness of Nirosta 4016/1.4016 ferritic steel for manufacturing interconnects in energy conversion electrochemical devices operating at 1073 K was confirmed. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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15 pages, 18665 KiB

Open AccessArticle

Crystallographic and TEM Features of a TBC/Ti₂AlC MAX Phase Interface after 1300 °C Burner Rig Oxidation

by James L. Smialek, Anita Garg, Bryan J. Harder and Michael D. Cuy

Crystals 2023, 13(4), 691; https://doi.org/10.3390/cryst13040691 - 17 Apr 2023

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Abstract

A FIB/STEM interfacial study was performed on a TBC/Ti₂AlC MAX phase system, oxidized in an aggressive burner rig test (Mach 0.3 at 1300 °C for 500 h). The 7YSZ TBC, α-Al₂O₃ TGO, and MAXthal 211^TM Ti₂ [...] Read more.

A FIB/STEM interfacial study was performed on a TBC/Ti₂AlC MAX phase system, oxidized in an aggressive burner rig test (Mach 0.3 at 1300 °C for 500 h). The 7YSZ TBC, α-Al₂O₃ TGO, and MAXthal 211^TM Ti₂AlC base were variously characterized by TEM/STEM, EDS, SADP, and HRTEM. The YSZ was a mix of “clean” featureless and “faulted” high contrast grains. The latter exhibited ferro-elastic domains of high Y content tetragonal t″ variants. No martensite was observed. The TGO was essentially a duplex α-Al₂O₃ structure of inner columnar plus outer equiaxed grains. It maintained a perfectly intact, clean interface with the Ti₂AlC substrate. The Ti₂AlC substrate exhibited no interfacial Al-depletion zone but, rather, numerous faults along the basal plane of the hexagonal structure. These are believed to offer a means of depleting Al by forming crystallographic, low-Al planar defects, proposed as Ti_2.5AlC_1.5. These characterizations support and augment prior optical, SEM, and XRD findings that demonstrated remarkable durability for the YSZ/Ti₂AlC MAX phase system in aggressive burner tests. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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Review

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21 pages, 2926 KiB

Open AccessReview

Review on the Corrosion Behaviour of Nickel-Based Alloys in Supercritical Carbon Dioxide under High Temperature and Pressure

by Yiyao Kang, Xuesong Leng, Lin Zhao, Bowen Bai, Xiaoya Wang and Hongsheng Chen

Crystals 2023, 13(5), 725; https://doi.org/10.3390/cryst13050725 - 25 Apr 2023

Cited by 6 | Viewed by 1954

Abstract

Supercritical carbon dioxide (S-CO₂) has the advantages of amphoteric liquid and gas, which possesses many unique characteristics, such as good compressibility, high density, high solubility, good fluidity and low viscosity. The Brayton cycle with S-CO₂ is considered to have many [...] Read more.

Supercritical carbon dioxide (S-CO₂) has the advantages of amphoteric liquid and gas, which possesses many unique characteristics, such as good compressibility, high density, high solubility, good fluidity and low viscosity. The Brayton cycle with S-CO₂ is considered to have many promising applications, especially for power conversion industries. However, the corrosion and degradation of structural materials hinder the development and application of the Brayton cycle with S-CO₂. Nickel-based alloys have the best corrosion resistance in S-CO₂ environments compared to austenitic stainless steels and ferritic/martensitic steels. Thus, the present article mainly reviews the corrosion behaviour of nickel-based alloys in S-CO₂ under high temperature and pressure. The effect of alloying elements and environment parameters on the corrosion behaviour of different nickel-based alloys are systematically summarized. The conclusion and outlook are given at the end. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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