Selection of Superalloys for Design

Donachie, Matthew J.; Donachie, Stephen J.

doi:10.1002/9780470172551.ch10

Cited by 13 publications

(24 citation statements)

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“…The expected microstructures from each condition are listed in Table II. In Inconel 718, γ' is spherical in shape having an ordered fcc structure, and γ" is disc in shape having a bct structure, while δ has an orthorhombic structure [9].A subset of the seven sample conditions was studied and reported here., i.e. the solutionized, peak-aged and over-aged conditions.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Chandrasekar¹,

Lo²,

Frishman³

et al. 2012

AIP Conference Proceedings

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This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity. ABSTRACT. This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity.

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Section: Microstructural Characterizationmentioning

confidence: 99%

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Chandrasekar¹,

Lo²,

Frishman³

et al. 2012

AIP Conference Proceedings

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“…Thus, the recent trend is for a higher concentration of tungsten and reduction in the molybdenum concentration to increase solid solution strengthening and coarsening of the gamma prime (γ') precipitates. The volume fraction of gamma prime slightly reduces with an increase in concentration of titanium, niobium and tantalum, but increases the antiphase boundary (explained in section 2.2.2) and mismatch between the precipitate and the matrix (γ'/γ) [12].…”

Section: Nickel-base Superalloys: Chemistry and Microstructurementioning

confidence: 99%

“…Superalloys derive their strength through solid solution strengthening and in some alloys through precipitation hardening [12]. The nickel based superalloys which are used in the high temperature zones of a gas turbine always contain a certain amount of aluminum and chromium, which form protective oxides of alumina (Al2O3) and chromia (Cr2O3), thereby preventing further removal of the material in a harsh environment.…”

Section: Application Of Nickel-based Superalloysmentioning

confidence: 99%

“…The iron-base superalloys are the most underdeveloped alloys in the field of superalloys because of their low mechanical strength compared to nickel and cobalt-base superalloys, but they are very resistant to corrosion and oxidation [12].…”

Section: Iron-base Superalloysmentioning

confidence: 99%

“…However, there are number of drawbacks to iron-base superalloys. First, the electronic structure of iron has a greater tendency to promote the formation of brittle TCP phases (σ and Laves) other than the ordered FCC -L12 γ' (gamma prime) phase, which when often at best only metastable [12] [21]. Second, replacement of nickel by iron as the base element decreases the oxidation resistance.…”

Section: Iron-base Superalloysmentioning

confidence: 99%

See 2 more Smart Citations

Isothermal Oxidation Comparison of Three Ni-Based Superalloys

Mallikarjuna

Richards

Caley

2017

J. of Materi Eng and Perform

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Characterization of Plastic Flow Pertinent to the Evolution of Bulk Residual Stress in Powder-Metallurgy, Nickel-Base Superalloys

Semiatin

Fagin

Goetz

et al. 2015

Metall Mater Trans A

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The plastic-flow behavior which controls the formation of bulk residual stresses during final heat treatment of powder-metallurgy (PM), nickel-base superalloys was quantified using conventional (isothermal) stress-relaxation (SR) tests and a novel approach which simulates concurrent temperature and strain transients during cooling following solution treatment. The concurrent cooling/straining test involves characterization of the thermal compliance of the test sample. In turn, this information is used to program the ram-displacement-vs-time profile to impose a constant plastic strain rate during cooling. To demonstrate the efficacy of the new approach, SR tests (in both tension and compression) and concurrent cooling/tension-straining experiments were performed on two PM superalloys, LSHR and IN-100. The isothermal SR experiments were conducted at a series of temperatures between 1144 K and 1436 K (871°C and 1163°C) on samples that had been supersolvus solution treated and cooled slowly or rapidly to produce starting microstructures comprising coarse gamma grains and coarse or fine secondary gamma-prime precipitates, respectively. The concurrent cooling/straining tests comprised supersolvus solution treatment and various combinations of subsequent cooling rate and plastic strain rate. Comparison of flow-stress data from the SR and concurrent cooling/ straining tests showed some similarities and some differences which were explained in the context of the size of the gamma-prime precipitates and the evolution of dislocation substructure. The magnitude of the effect of concurrent deformation during cooling on gamma-prime precipitation was also quantified experimentally and theoretically.

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Selection of Superalloys for Design

Cited by 13 publications

References 0 publications

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Isothermal Oxidation Comparison of Three Ni-Based Superalloys

Characterization of Plastic Flow Pertinent to the Evolution of Bulk Residual Stress in Powder-Metallurgy, Nickel-Base Superalloys

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