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Microstructural Degradation of Superalloys during Service: Mechanical and/or Corrosion

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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (15 December 2021) | Viewed by 8027

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Special Issue Editors

Prof. Dr. Yanhui Chen

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Guest Editor

Beijing Key Lab of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China
Interests: in situ; TEM; superalloy; microstructure; turbine blade

Prof. Dr. Yunsong Zhao

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Guest Editor

Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095, China
Interests: superalloy; creep; microstructure; grain boundary; single crystals

Special Issue Information

Dear Colleagues,

Superalloys used as blade material for gas turbines are strengthened by small intermetallic γ'-precipitates of the Ni₃Al type. γ'-precipitation provides excellent mechanical properties at high temperatures, but its efficiency strongly depends on the size and morphology of the γ'-precipitates. During high temperature service in aircraft and power gas turbines, the γ/γ'-microstructure of nickel-base superalloys gradually degrades, i.e., coarsens and becomes rafted. This degradation of the microstructure deteriorates the mechanical properties. The relationship between microstructure and its properties are thus important to evaluate the service of the blade.

In this thematic issue, we invite contributions on the microstructure degradation of superalloys and the microstructural characterization and relationships between microstructure and its properties. The submitted works are expected to feature but are not limited to the following topics:

Microstructural characterization of superalloys;
Relationship between microstructural variation and its properties;
Microstructural variation during corrosion of superalloys;
Stress corrosion induced microstructural degradation in superalloys;
Evaluation of serviced turbine blade;
Newly developed superalloys: high entropy alloys, etc.

Prof. Dr. Yanhui Chen
Prof. Dr. Yunsong Zhao
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. Crystals 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
superalloys
degradation
creep
oxidation

Published Papers (4 papers)

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Research

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10 pages, 3243 KiB

Open AccessArticle

Effect of Low-Angle Boundaries on the Microstructures and Tensile Properties of the Third-Generation Single-Crystal Superalloy DD9

by Wanpeng Yang, Jiarong Li, Shizhong Liu, Xiaoguang Wang, Jinqian Zhao and Zhenxue Shi

Crystals 2022, 12(5), 595; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12050595 - 24 Apr 2022

Cited by 2 | Viewed by 1362

Abstract

The microstructure of low-angle boundaries (LABs) of thethird-generation single-crystal superalloy DD9 and its effect on the tensile properties at 1100 °C were investigated. Double seed crystals techniques were used to obtain the specimens of DD9 alloy with LABs. The results show thatthe as-cast LABs of DD9 alloy are composed of strip-like and bulk γ′ phases with γ matrix, while no γ′ phases were foundat the LABs after the heat treatment. The LABs had little effect on the tensile strength of DD9 alloy, but hadan obvious effect on the tensile plasticity, and the fracture surfaces of tensile-ruptured DD9 alloy with LABs of 3.7°~11.4° exhibited intergranular fracture features at 1100 °C. Full article

(This article belongs to the Special Issue Microstructural Degradation of Superalloys during Service: Mechanical and/or Corrosion)

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7 pages, 13960 KiB

Open AccessCommunication

Effect of Service-Induced Degradation on Residual Stress Rupture Life of a Directionally Solidified Superalloy

by Xiaotong Guo, Weijie Xing, Heng Zhang, Yong Li, Hemeng Peng and Chuan Yang

Crystals 2022, 12(2), 267; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020267 - 16 Feb 2022

Cited by 1 | Viewed by 1505

Abstract

The influence of service-induced degradation on residual life is very important for the safe service of turbine blades. In this study, a series of simulation experiments were conducted on a directionally solidified superalloy under (880–1020) °C/(70–220) MPa and interrupted after 500 h. Then, the stress rupture life of the interrupted specimens was tested under 980 °C/275 MPa. The results showed that the increase of simulated experiment temperature decreased the residual stress rupture life. In brief, the simulation experiments at 880 °C did not influence the residual stress rupture life of the alloy. The simulated experiments at 980 °C and 1050 °C mainly affected the microstructure of γ’ phase, while not γ/γ’ eutectic and carbides. After the stress rupture tests under 980 °C/275 MPa, cracks were located at the interfaces between carbides and γ matrix in the interdendritic regions. This study provides guidance on the degradation evaluation and safety service of the directionally solidified superalloys. Full article

(This article belongs to the Special Issue Microstructural Degradation of Superalloys during Service: Mechanical and/or Corrosion)

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8 pages, 4909 KiB

Open AccessCommunication

Effect of Overheating Temperature on Thermal Cycling Creep Properties of K465 Superalloy

by Xiaotong Guo, Zeshan Liang, Xiaobin Nan, Chunxu Jiang, Yong Li, Li Li, Liang He and Shizheng Yang

Crystals 2021, 11(12), 1458; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11121458 - 25 Nov 2021

Cited by 2 | Viewed by 1241

Abstract

Turbine blades in aircraft engines may encounter overheating and suffer serious creep property degradation. In this study, the thermal cycling creep experiments were conducted on K465 superalloy under (900 °C/30 min–1100 °C/3 min)/50 MPa, (900 °C/30 min–1150 °C/3 min)/50 MPa and (1000 °C/30 min–1150 °C/3 min)/50 MPa. The investigated thermal cycling creep properties were dramatically degraded, and increasing the overheating temperatures significantly decreased the thermal cycling creep life. The secondary γ′ precipitates obviously dissolved and the area fraction decreased to around 35.2% under (900 °C/30 min–1150 °C/3 min)/50 MPa and (1000 °C/30 min–1150 °C/3 min)/50 MPa, which was almost half that after the standard solution treatment. The decline of the thermal cycling creep properties was mainly due to the significant dissolution of γ′ precipitates. The creep holes/cracks were mainly distributed at the M₆C carbides and γ/γ′ eutectics interfaces, M₆C carbides and γ′ film interfaces in the grain boundaries, and resulted in the final intergranular fracture. Full article

(This article belongs to the Special Issue Microstructural Degradation of Superalloys during Service: Mechanical and/or Corrosion)

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Review

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17 pages, 12818 KiB

Open AccessEditor’s ChoiceReview

Application of Hot Isostatic Pressing in Nickel-Based Single Crystal Superalloys

by Yunsong Zhao, Siliang He and Longfei Li

Crystals 2022, 12(6), 805; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060805 - 07 Jun 2022

Cited by 6 | Viewed by 3107

Abstract

Hot isostatic pressing (HIP) technology can effectively reduce microstructure defects such as micropores, which are formed during solidification and hominization heat treatment, and thus further improve the high temperature performance of nickel-based SX superalloys. This paper reviews the application of HIP treatment in nickel-based SX superalloys, focusing on the dislocation-creep closure and diffusion-creep closure mechanisms and the kinetics of annihilation of micropores by HIP. The effects of different scheme on pore closure and high temperature mechanical properties are compared. The advantages and disadvantages of different schemes are summarized. In addition, the application of HIP treatment in additive manufacturing (AM) of nickel-based SX superalloys is also discussed. Full article

(This article belongs to the Special Issue Microstructural Degradation of Superalloys during Service: Mechanical and/or Corrosion)

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