The Effect of Cooling Rate After Full Solution and Aging Time on Microstructure and Hardness of IN718 Superalloy Fabricated via SLM

IN718 alloy is a high strength Nickel base superalloy that mainly used in moderate temperatures and corrosive service conditions. In the present study, samples produced by selective laser melting (SLM) at 1040 °C for 120 minutes were prepared under solution treatment. After solution, the samples were cooled in three cooling media of water, air and extinguished furnace with open door. Finally, the samples were aged in three standard conditions for 48 and 72 hours. To investigate the effect of cooling rate after solution and aging time on precipitates characteristics and microstructure of samples, Field Emission Scanning Electron Microscope (FESEM), X-ray diffraction (XRD) and hardness test were used. The results showed that increasing the aging time under constant solution conditions increases the volume fraction and the size of the secondary phases. Also, reducing the cooling rate in the solution step leads to increasing the hardness of the samples in the aging stage. Finally, with increasing aging time, the maximum hardness of the sample was 794H. v.