Metallurgical optimisation of PM superalloy N19
1 Onera – The French Aerospace Lab, 92322 Châtillon, France
2 MINES ParisTech, Centre des Matériaux CNRS UMR 7633, BP. 87, 91003 Evry Cedex, France
3 Snecma Gennevilliers, 171 Bld. Valmy, BP. 31, 92702 Colombes Cedex, France
4 Snecma Villaroche, 77550 Moissy-Cramayel, France
a Corresponding author: firstname.lastname@example.org
Microstructures of the new PM superalloy N19 have been investigated for various heat treatments in order to reach the best compromise between static strength and cyclic resistance. One subsolvus and several supersolvus heat treatments were applied to produce fine (7 μm) and medium (25 μm) grain sizes, respectively. The alloy is shown to be quite sensitive to the cooling conditions after solutioning as the γ′ hardening precipitates, both secondary and tertiary, have a direct influence on mechanical properties. Two cooling conditions after solutioning produce a high crack propagation resistance at 650 °C with dwell time cycles, which is one of the basic requirements. The low cycle fatigue behaviour appears to be correlated to the grain size, which determines the origin of crack initiation (from ceramic inclusions or not). The other mechanical properties (tensile, creep) remain above target levels. Despite the medium size grain microstructure in the supersolvus condition, a high level of mechanical strength is observed in N19 at elevated temperature. It is understood that further improvement in properties can be achieved by developing coarse grain microstructures.
© Owned by the authors, published by EDP Sciences, 2014
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