The effect of aging process at 845° C for 24 h and casting conditions on the microstructure andmechanical properties ofNi base superalloyswere 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 decreaseswith 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 ãÂ particles in case of aged with lowsuperheat specimen is higher than that in high superheat one after solution at 1120 and 1180° C. The Vf of ãÂ 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 lowand high superheat specimens solution treated at 1120° C are higher than that of 1180° C.