The solution treatment process has been carried out on Ni-based HR-120 superalloy (Fe-40Ni-24Cr) at six different temperatures, namely 950ºC, 1000ºC, 1050ºC, 1100ºC, 1150ºC and 1200ºC. All samples were soaking for 3 hours at desired temperature, followed by water quench. The main objective of the solution treatment process is to vary the grain size of the alloy. The effect of solution treatment process on the alloy has been investigated in term of microstructure, grain size, phase present and hardness test, by using optical microscope, scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer, x-ray diffraction (XRD) technique and Vickers hardness test. As a results, the grain size of the solution-treated alloy were increase as the solution treatment temperature increase from 27.27 μm to 40.86 μm for solution-treated alloy at 950ºC to 1200ºC, respectively. Three precipitate phases were detected during phase analysis which are NbC, TiC and (Nb,Ti)C on the solution-treated alloy. In addition, as the grain size increase when the solution treatment temperature increase, the hardness value was decrease.
