Microstructural design and optimization of Nickel-based superalloys for gas turbines

Abstract: One of the main sources of energy in this modern world is the gas turbine.  They reach extremely high working temperatures at peak capacity and hence require materials that can withstand the same.  Nickel-based superalloys have been widely used as working materials due to their various high-temperature properties, which help protect them from oxidation, corrosion,  and  creep.  This  high-temperature  strength  is  provided by the  gamma  prime (γ′)  phase  for  most  nickel-based  alloys.  This  study  deals  with understanding  the  effect of the mean γ′ phase size affected by different times and temperatures.  Different trial alloys have undergone different primary ageing cycles, followed by a subsequent secondary ageing  cycle.  Further,  the  mean  gamma  prime size  calculated  using  Image-Pro  coupled with  a  probability  density  function  for the mean  size  showed  significant  γ′  coarsening. Different temperatures and holding times also allowed for significant growth of secondary gamma prime structures.  These structures were found to impact the mean gamma prime size calculations significantly with their influence on the mechanical properties remaining unknown.  However, the mean gamma prime size remains similar to what was desired.