Dresden 2003 – scientific programme

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M: Metallphysik

M 31: Intermetallische Phasen I

M 31.4: Talk

Wednesday, March 26, 2003, 15:30–15:45, IFW B

MICROSTRUCTURAL CHARACTERIZATION OF INCONEL 706 ALLOY — •Vitaliy Kindrachuk¹, Nelia Wanderka¹, John Banhart¹, Debashis Mukherji², Dominique Del. Genovese², and Joachim Roesler² — ¹Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin, Germany — ²Technical University Braunschweig, D-38106 Braunschweig, Germany

Inconel 706 is a wrought Ni-Fe base superalloy which is used for high temperature services, e.g. for gas turbine discs. It is age-hardened by precipitation of coherent g’ and/or g” in the austenitic matrix g. However, the microstructure is strongly dependent on the age-hardening treatment. Direct ageing produces individual g’ and g” precipitates and g’ - g” co-precipitates, while a three step heat treatment, in addition produces h precipitates mainly at the grain boundary. Characterization of the precipitates and matrix was carried out by three-dimensional atom probe tomography and by high resolution transmission electron microscopy. After direct ageing the precipitates with average size of about 10 nm are generally smaller than that after the stabilizing heat treatment of about 20 nm. In addition, much bigger individual g” precipitates with sizes above 50 nm were also observed. They are semi-coherent with the matrix and are oriented parallel to the <001> lattice direction of the g matrix. While the g’-phase is enriched in Ni, Al, Ti and Nb the g”-phase contains only little Al, and is enriched in Ti and Nb.