The effect of aging process at 845° C for 24 h and casting conditions on the microstructure and
mechanical properties of Ni base superalloys were investigated. Alloys under investigation were
manufactured by investment casting under various conditions of cooling rate and superheat.
These alloys were solution treated at 1120 and 1180° C followed by air cooling before aging
process. The volume fraction of TCP phases decreases with increasing casting superheat and
lowering cooling rate. The grain size of aged specimens and solution treated at 118°0 C is
coarser than ones solution treated at 1120° C. The Vf of γ’ particles in case of aged with low
superheat specimen is higher than that in high superheat one after solution at 1120 and 1180° C.
The Vf of γ' in case of aged and solution treated at 1120° C is higher than that aged with
solution treated at 1180° C. Hardness measurements of aged alloys with low and high superheat
specimens solution treated at 1120° C are higher than that of 1180° C.