Effect of rejuvenation heat treatments on gamma prime distributions in a Ni based superalloy for power plant applications

The gamma prime (γ′) distribution in the Ni based superalloy, CMSX-4, has been examined in detail using a field emission gun scanning electron microscope and a transmission electron microscope after high temperature degradation and the subsequent application of a number of rejuvenation heat treatments. The observed microstructures have been studied in order to explain the observed mechanical properties of the material and also to assess the effectiveness of the heat treatment procedures and their effect on the subsequent mechanical performance. It is shown that there are significant differences in the rafting behaviour and the size of the channels between the γ′ particles and the size of the tertiary γ′ particles in each of the different microstructural conditions. The aim of this research is to provide greater understanding of the suitability of rejuvenation heat treatments and their role in the extension of component life in power plant applications.