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Metals
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Study of Microstructure Evolution and Deformation Behavior of Superalloys
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Study of Microstructure Evolution and Deformation Behavior of Superalloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Structural Integrity of Metals".

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 8471

Special Issue Editors

Prof. Dr. Lei Zheng

grade E-Mail Website
Guest Editor
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
Interests: design, research and application of superalloys
Special Issues, Collections and Topics in MDPI journals
Dr. Xuezhi Qin

E-Mail Website
Guest Editor
Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Interests: superalloys; chemical composition design; relationship among chemical composition, microstructure, and properties; thermal expansion behavior; damage assessment and life prediction of hot end components; superalloys for the hot end components of gas turbines; superalloys for nuclear reactors and reprocessing; superalloys for the petrochemical industry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Superalloys are advanced structural materials that are mainly used in aircraft engines and also extensively applied in chemical, petrolic, and electrical industries. They are generally strengthened by second phases, such as γ', γ", carbides, etc. Microstructure and its evolution are the decisive factors of the properties of superalloys. Deformation is the important process for preparing products and affecting microstructure at the same time. Advances in superalloys, which include microstructure evolution and deformation behavior, are within the scope of this Special Issue. Their influences on the mechanical, physical, and chemical properties are suitable as well. The results or methods improving the microstructure stability and temperature capacity are typically welcomed.

Prof. Dr. Lei Zheng
Dr. Xuezhi Qin
Guest Editors

Manuscript Submission Information

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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

  • microstructure
  • wrought
  • cast
  • powder metallurgy
  • precipitation
  • aging
  • oxidation
  • strain–stress curve
  • recrystallization
  • deformation

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Published Papers (4 papers)

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Research

13 pages, 14805 KiB  
Article
Effect of Heat Treatment Schedules on Creep Performance of Ni-Based Superalloy Mar-M247 at 871 °C and 250 Mpa
by Qinghai Pan, Yongfeng Sui, Peijiong Yu, Xinbao Zhao, Yuan Cheng, Quanzhao Yue, Yuefeng Gu and Ze Zhang
Metals 2023, 13(7), 1270; https://doi.org/10.3390/met13071270 - 14 Jul 2023
Cited by 1 | Viewed by 1755
Abstract
The effects of heat treatment (H1 and H2) on the creep behavior and microstructures of Mar-M247 at 871 °C/250 MPa are studied. The results show that the as-cast microstructure is composed of eutectics, γ phase, γ’ phase, MC and M23C6 [...] Read more.
The effects of heat treatment (H1 and H2) on the creep behavior and microstructures of Mar-M247 at 871 °C/250 MPa are studied. The results show that the as-cast microstructure is composed of eutectics, γ phase, γ’ phase, MC and M23C6 carbides, while new M6C appears in heat-treated microstructures, indicating the transformation of carbides after heat treatments. The Mar-M247 is excellent, with over 1500 h of creep life, and H1 is 48% higher than H2. The addition of post-brazing and diffusion heat treatment in H2 is detrimental to creep resistance; the two steps promoted the transformation of MC into M23C6 in advance. The increase and coarsening of M23C6 would consume more γ-phase-forming elements, weakening the solution strengthening at grain boundaries. As a result, the resistance of the grain boundary and γ/γ’ interface to dislocation motion is significantly reduced, leading to the cracks’ initiation and propagation along the grain boundaries. Full article
(This article belongs to the Special Issue Study of Microstructure Evolution and Deformation Behavior of Superalloys)
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14 pages, 40263 KiB  
Article
Oxidation Property of a Fourth-Generation Powder Metallurgy FGH4108 Nickel-Based Superalloy
by Xin Zhao, Zhigang Wang, Jinjuan Lv, Xiao Liu, Lei Zheng and Jiantao Liu
Metals 2023, 13(5), 945; https://doi.org/10.3390/met13050945 - 13 May 2023
Cited by 6 | Viewed by 2069
Abstract
Isothermal oxidation kinetics of a fourth-generation powder metallurgy FGH4108 nickel-based superalloy is investigated at 800 °C to 1100 °C by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). At 800 °C and 900 °C, the oxidation kinetic curves [...] Read more.
Isothermal oxidation kinetics of a fourth-generation powder metallurgy FGH4108 nickel-based superalloy is investigated at 800 °C to 1100 °C by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). At 800 °C and 900 °C, the oxidation kinetic curves of the FGH4108 superalloy follow parabolic law. At 1000 °C, the oxidation kinetic curve follows cubic law. At 1100 °C, the oxidation kinetic curve has two distinct parts: the first part follows a parabolic law, and the second one obeys a linear law. Cross-sectional morphologies and elemental distributions show that the oxide film consists of two parts at 800 °C: the outer layer is a continuous dense protective Cr2O3 oxide film, and the inner layer is a discontinuous Al2O3 oxide layer. At 900–1100 °C, the oxides consist of three layers: the outermost is the oxides of Cr2O3 and TiO2, the middle is a continuous oxide of Al2O3, and the innermost is dotted oxides of TiO2. The thickness of the inner TiO2 oxide layer increases with the increase of oxidation temperature. On this basis, the oxidation behavior of the FGH4108 superalloy at high temperatures is confirmed to be controlled by the diffusion of Cr, Al, Ti, and O. From the aspect of oxidation resistance, the long-term service temperature of the FGH4108 superalloy should not exceed 1000 °C. Full article
(This article belongs to the Special Issue Study of Microstructure Evolution and Deformation Behavior of Superalloys)
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12 pages, 3625 KiB  
Article
Cracking during High-Temperature Deformation of a High-Strength Polycrystalline CoNi-Base Superalloy
by Daniel Hausmann, Lisa Patricia Freund, Cecilia Solís, Sven Giese, Mathias Göken, Ralph Gilles and Steffen Neumeier
Metals 2022, 12(9), 1520; https://doi.org/10.3390/met12091520 - 14 Sep 2022
Viewed by 1896
Abstract
The crack susceptibility during processing has a crucial influence on the workability of wrought alloys. In particular, the processing of high-strength alloys that are prone to cracking is challenging and various process parameters have to be optimized to achieve a good formability. The [...] Read more.
The crack susceptibility during processing has a crucial influence on the workability of wrought alloys. In particular, the processing of high-strength alloys that are prone to cracking is challenging and various process parameters have to be optimized to achieve a good formability. The polycrystalline CoNi-base superalloy CoWAlloy1 provides a high potential for high-temperature applications due to it having a large forging window, a high γ′ fraction and excellent creep properties. In order to study its formability during hot rolling, its deformation behavior and susceptibility to cracking were characterized by sub- and supersolvus compression tests at temperatures between 1000–1150 °C. At temperatures around the γ′ solvus temperature, no cracks formed during the compression testing, while at lower temperatures, cracking occurred. Additionally, an in-situ high-temperature small-angle neutron scattering revealed the phase fractions and the precipitate size distributions at different processing temperatures. It was found that a high fraction of γ′ forms during cooling and cracking starts at the surface of the bar, when the hot bar encounters the cold rolls during hot rolling. Apparently, the precipitation of γ′, which causes a high strength and reduced ductility, and the absent recrystallization leads to pronounced crack propagation and limited formability below the γ′ solvus temperature. Full article
(This article belongs to the Special Issue Study of Microstructure Evolution and Deformation Behavior of Superalloys)
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20 pages, 3999 KiB  
Article
Near-Surface and Bulk Dissolution Behavior of γ′ Precipitates in Nickel-Based VDM® Alloy 780 Studied with In-Situ Lab-Source and Synchrotron X-ray Diffraction
by Frank Kümmel, Massimo Fritton, Cecilia Solís, Armin Kriele, Andreas Stark and Ralph Gilles
Metals 2022, 12(7), 1067; https://doi.org/10.3390/met12071067 - 22 Jun 2022
Cited by 4 | Viewed by 1842
Abstract
The dissolution of nano-sized Ni3Al-based γ′ precipitates was investigated in the newly developed polycrystalline nickel-based VDM® Alloy 780 at the surface and in the bulk region with in-situ lab-source and synchrotron X-ray diffraction. These studies are important in obtaining a deeper understanding [...] Read more.
The dissolution of nano-sized Ni3Al-based γ′ precipitates was investigated in the newly developed polycrystalline nickel-based VDM® Alloy 780 at the surface and in the bulk region with in-situ lab-source and synchrotron X-ray diffraction. These studies are important in obtaining a deeper understanding of the strengthening mechanism responsible for the stability and long service lives of such superalloys. We found that the dissolution behavior of the γ′ phase is very similar at the surface and in the bulk region, but small deviations were detected. The dissolution of γ′ starts at around 800 °C and no γ′ was found at temperatures exceeding 970 °C. As a result, the elements Al and Nb, which were bound in the γ′ phase, dissolved into the γ matrix and strongly increased the γ lattice parameter, as their atomic size is larger than the γ-forming elements Ni, Co, and Cr. However, this effect was suppressed in the surface area. A second matrix γ phase was detected at the same temperature range as that of the dissolution of the γ′ phase in the lab-source XRD measurements. The newly formed γ-2 phase had a smaller lattice parameter than that of the initial γ matrix. We propose that the γ-2 matrix phase is a result of high-temperature surface oxidation, which consumes, among other elements, Al and Nb and, therefore, leads to the smaller γ lattice parameter. Full article
(This article belongs to the Special Issue Study of Microstructure Evolution and Deformation Behavior of Superalloys)
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