DISSOLUTION BEHAVIOUR OF PRECIPITATES IN IN738LC

Super alloys are basically used in high temperature industrial applications due to their resistance to aggressive environments and longer durability than other conventional alloys. In this research, the dissolution behavior of primary gamma prime precipitates has been analyzed under various solution heat treatments via making changes in the time and temperature of the Standard Heat Treatment (SHT) and subjecting the specimens to external compressive stress. The microstructures were examined by Scanning Electron Microscope (SEM) and afterwards the diameters and the numbers of precipitates were measured. It could be seen from the SEM photos that the cubic precipitates has been agglomerated and their corners got rounded in order to make a spherical shape. The results showed that the best dissolution could be achieved by T>1200oc and t>2.5h. Additionally the system reached to equilibrium after 2.5 hours in any temperature hence by spending more time no changes in either morphology or the volume fraction could be observed. Although the small applied compressive stress has had a little effect on the process, it has helped the precipitates in agglomerating. On the contrary exposing the specimens to great compression has led to a continuous and uniform dissolution.