There is a worldwide drive to increase the efficiency of power plants in order to reduce the
amount of fossil fuel consumed and associated CO2 emissions. Raising the operating temperature
and pressure can improve the thermal efficiency, however, this necessitate the use of materials
which have high temperature performance. Steels are currently used at temperature up to 600°C
with the efficiency of 38-40 %. Advanced Ultra Supercritical (A-USC) design plans power plants
to operate at steam temperatures of 700°C and pressure up to 35 MPa with a lifetime of at least
100 000 hours. Ni-base superalloys are leading materials due to their significant strength and
creep resistance.
Haynes 282 is one possible candidate to meet the A-USC conditions for turbine engines. This
alloy is a γ′ precipitation strengthened material and exhibits very good creep properties and
thermal stability. The alloy examined in this research was produced by sand casting, and
therefore the aim of this research is to investigate the microstructural evolution in large scale cast
components.
The alloy has been examined in both the as-cast condition and as a function of a range of
different pre-service heat treatments. The microstructural changes during different heat treatments
have been fully identified and quantified. The results have also been compared with predictions
from thermodynamic equilibrium calculations using a Ni alloy database. It has been found that
variations in the heat treatment conditions can have a significant effect on microstructural
development and hence, potentially, the mechanical properties of Haynes 282 alloy
