Effect of heat treatment on the morphology and mechanical properties of the novel Ni-based superalloy with machinability assessment through electrical discharge machining

A superalloy is a high-performance alloy used for achieving stability and strength at elevated temperatures. The present work aims at investigating heat treatment characteristics of a single crystal Nickel-based superalloy used in aero turbine blades in order to check any improvement in property at high temperatures. In the current work, the alloy is subjected to heat treatment at various temperatures such as 950 °C, 1000 °C, 1100 °C, 1200 °C and 1300 °C. It is found that as aging temperature increases the γ’ precipitates diffuse between themselves and form larger cuboidal γ’ (Gamma prime) structures in the superalloy matrix. The larger γ’ phase indicates higher creep strength of the superalloy. Again, through electrical discharge machining, process parameters such as voltage gap (V g ), pulse on time (T on ) and flushing pressure (F p ) are chosen to determine the tool wear rate (TWR), material removal rate (MRR) and surface roughness (SR) of the superalloy. RSM (response surface methodology) along with GRA (grey-relational analysis) is adopted in order to design a model and optimize the process parameters. It is observed that V g has the most significant effect on the machining process as a whole. It is experimentally validated that V g of 80 V, T on of 100 µs, and F p of 0.5758 kg/mm 2 bear the optimal values for the multi-responses. The predicted optimized results of TWR, MRR, SR and grey-relational grade are well fitted with optimized experimental values having a percentage of error <5%.