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Download fileMicrostructural evolution in a nickel based superalloy for power plant applications as a consequence of high temperature degradation and rejuvenation heat treatments
conference contribution
posted on 2014-03-12, 15:27 authored by Zhiqi Yao, Mark JepsonMark Jepson, Rachel ThomsonRachel Thomson, C.C. DegnanThe microstructural evolution of the Ni-based superalloy CMSX-4 including the change in
gamma prime size and distribution and the degree of rafting has been examined in detail using
field emission gun scanning electron microscopy (FEGSEM) and transmission electron
microscopy (TEM) after high temperature degradation and rejuvenation heat treatments. The
relationship between the microstructure, mechanical properties and the applied heat treatment
procedures has been investigated. It is shown that there are significant differences in the rafting
behaviour, the size of the ‘channels’ between the gamma prime particles, the degree of rafting
and the size of the tertiary gamma prime particles in each of the different microstructural
conditions studied. Chemical segregation investigations were carried out to establish the cause of
reduced mechanical properties of the rejuvenated sample after high temperature degradation
compared to an as-received sample after the same degradation procedure. The results indicate that
although the microstructure of as-received and rejuvenated samples were similar, the chemical
segregation was more pronounced in the rejuvenated samples, suggesting that chemical
segregation from partitioning of the elements during rejuvenation was not completely eliminated.
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.
Funding
The authors would like to acknowledge the support of the Technology Strategy Board (Project Number TP/5/MAT/6/I/H0101B) and the following companies: Alstom Power Ltd., E.ON New Build & Technology Limited, Doosan Babcock, National Physical Laboratory and QinetiQ for their valuable contributions to the project.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials