Stress relaxation behaviour in IN718 nickel based superalloy during ageing heat treatments

Salaheddin Rahimi, Michael King, Christian Dumont

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Designing microstructure of components made from Inconel 718 nickel based superalloy (IN718) with tailored mechanical properties for high temperature applications, require sequential thermo-mechanical processing. This often includes straining and annealing at solution annealing temperature (i.e. ≈980℃) followed by water quenching and subsequent aging heat treatments at lower temperatures. In addition to the microstructure development (i.e. precipitation) the aging heat treatment partially relieve the residual stresses generated at previous stages of forging and water quenching, however the stress field will not be completely relaxed. In this study, a series of experiments were conducted on round tensile specimens made from IN718 bar to investigate tensile stress relaxation behaviours at elevated temperatures used for aging heat treatments. The stress relaxation curves obtained can be described by a hyperbolic function with a non-zero asymptotic stress (σ∞), which seems to be proportional to the initially applied stress (σ0) for a fixed temperature. This behaviour is investigated at temperatures between 620℃ and 770℃ that is a temperature range used in industry to perform the aging heat treatments to obtain microstructures with tailored mechanical properties. It has been shown that the σ∞/ σ0 ratio has decreased rapidly with increasing temperature at this range. The relaxation behaviour has been assessed numerically and an empirical relationship has been defined for each temperature that can be used for modelling purposes.
LanguageEnglish
Pages563-573
Number of pages22
JournalMaterials Science and Engineering: A
Volume708
Early online date28 Sep 2017
DOIs
Publication statusPublished - 21 Dec 2017

Fingerprint

stress relaxation
heat resistant alloys
Stress relaxation
Nickel
Superalloys
heat treatment
Aging of materials
Heat treatment
nickel
Temperature
temperature
microstructure
Microstructure
quenching
Quenching
mechanical properties
hyperbolic functions
Inconel (trademark)
Annealing
annealing

Keywords

  • stress Relaxation
  • residual Stress
  • IN718
  • mechanical Properties
  • superalloy

Cite this

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title = "Stress relaxation behaviour in IN718 nickel based superalloy during ageing heat treatments",
abstract = "Designing microstructure of components made from Inconel 718 nickel based superalloy (IN718) with tailored mechanical properties for high temperature applications, require sequential thermo-mechanical processing. This often includes straining and annealing at solution annealing temperature (i.e. ≈980℃) followed by water quenching and subsequent aging heat treatments at lower temperatures. In addition to the microstructure development (i.e. precipitation) the aging heat treatment partially relieve the residual stresses generated at previous stages of forging and water quenching, however the stress field will not be completely relaxed. In this study, a series of experiments were conducted on round tensile specimens made from IN718 bar to investigate tensile stress relaxation behaviours at elevated temperatures used for aging heat treatments. The stress relaxation curves obtained can be described by a hyperbolic function with a non-zero asymptotic stress (σ∞), which seems to be proportional to the initially applied stress (σ0) for a fixed temperature. This behaviour is investigated at temperatures between 620℃ and 770℃ that is a temperature range used in industry to perform the aging heat treatments to obtain microstructures with tailored mechanical properties. It has been shown that the σ∞/ σ0 ratio has decreased rapidly with increasing temperature at this range. The relaxation behaviour has been assessed numerically and an empirical relationship has been defined for each temperature that can be used for modelling purposes.",
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Stress relaxation behaviour in IN718 nickel based superalloy during ageing heat treatments. / Rahimi, Salaheddin; King, Michael; Dumont, Christian.

In: Materials Science and Engineering: A, Vol. 708, 21.12.2017, p. 563-573.

Research output: Contribution to journalArticle

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