Aging of the Inconel 718 alloy between 500 and 750{degree}C
- Laboratoire de Structure des Materiaux Metalliques, Universite de Paris-Sud, Batiment 414, 91405 Orsay Cedex (France)
- Laboratoire de Metallurgie Structurale, URA CNRS 1107, Universite de Paris-Sud, Batiment 414, 91405 Orsay Cedex (France)
The aging of the NC 19 Fe Nb alloy (Inconel 718), previously quenched from 990{degree}C, is characterized by a hardness peak at 650{degree}C, then a maximum in hardness at about 750{degree}C. Over this temperature, the hardness progressively decreases. In the 550{endash}650{degree}C temperature range, TEM observations have revealed that {beta} (Ni{sub 3}Nb) precipitates are formed as long platelets parallel between them within the same grain, as well as extremely fine {gamma}{sup {prime}}[Ni{sub 3}(Ti,Al)] particles responsible for the observed improvement in hardness. For a tempering temperature higher than 650{degree}C, a first hardening occurs after a 4 h treatment, which has been associated with the {gamma}{sup {prime}} phase precipitation, with a more or less spherical shape. Beyond this time, a second hardening takes place linked to the {gamma}{sup {prime}{prime}} phase precipitation (Ni{sub 3}Nb, bct D0{sub 22} structure), as thin platelet shaped, perfectly coherent with the matrix. The misfit between the {gamma} and {gamma}{sup {prime}{prime}} phases is about 3{percent} in the {l_angle}001{r_angle}{gamma}{sup {prime}{prime}} direction and lower than 1{percent} in the {l_angle}100{r_angle}{gamma}{sup {prime}{prime}} and {l_angle}010{r_angle}{gamma}{sup {prime}{prime}} directions. During a longer aging at 750{degree}C, the {gamma}{sup {prime}{prime}} platelets progressively dissolve while {beta} precipitates grow. {copyright} {ital 1997 Materials Research Society.}
- OSTI ID:
- 544823
- Journal Information:
- Journal of Materials Research, Vol. 12, Issue 9; Other Information: PBD: Sep 1997
- Country of Publication:
- United States
- Language:
- English
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