A new TEM method for the characterization of the tertiary γ′ nano-precipitates in a PM disk superalloy: influence of ageing

Abstract

An original method for characterizing the γ′-phase tertiary precipitates in a Ni-based superalloy manufactured by powder metallurgy is described. This investigation is made using post mortem transmission electron microscopy (TEM). It is based on the analysis of sheared areas within crept specimens, which allows the precipitates revealed by the dislocations in their glide plane to be observed. The characteristics of these nano-precipitates, i.e. their size, their volume fraction and the channel width between them, are determined for two different heat treatments (HTs). The results show a wide distribution of the microstructural parameters for a given HT, but only slight differences between the microstructures produced by the two different HTs. This microstructural information allows a better understanding of the wide variety of the deformation micromechanisms observed during creep at high temperature.

Acknowledgments

We are grateful for financial support from le Ministère de la Recherche, le Ministère de l’Equipement, des Transports et du Logement (programme RRIT “Recherche aéronautique sur le supersonique”).