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The Mechanism of Creep during Crack Propagation of a Superalloy under Fatigue–Creep–Environment Interactions

Authors
  • Wang, Minqing
  • Du, Jinhui
  • Deng, Qun
Type
Published Article
Journal
Materials
Publisher
MDPI AG
Publication Date
Oct 04, 2020
Volume
13
Issue
19
Identifiers
DOI: 10.3390/ma13194418
PMID: 33020419
PMCID: PMC7579000
Source
PubMed Central
Keywords
Disciplines
  • Article
License
Green

Abstract

In this study, we examine the mechanism of fatigue-crack propagation in 718Plus superalloy at 704 °C under fatigue–creep–environment interactions, in this case, a new turbine disc material used in aero-engines at high temperatures. The effect of creep on the fatigue-crack propagation of the superalloy at high temperature was also researched. There was an unusual inhibitory effect on the propagation of fatigue cracks in 718Plus alloy, in which the propagation rate of fatigue cracks decreased with the increase of creep time through exploration of dwell-fatigue-crack growth (DFCG) test with different creep times. In particular, under lower stress intensity factor range (Δ K ) conditions, the fatigue-crack growth rate with a 90 s hold-time was one order of magnitude lower than that with a 5 s hold-time. Conversely, the gap between the two DFCGs gradually decreased with the increase of Δ K and the creep effect became less apparent. The mechanism of crack propagation in 718Plus alloy under two creep conditions was investigated from a viewpoint of the microstructure, oxidation rate at high temperature and crack path morphology under different conditions.

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