Effect of solution temperature of rejuvenation heat treatment on the stability of ?? precipitates in Ni-base superalloy IN738LC during long-term heating

This study aims to investigate the effect of time and temperature of complete and partial solutionizing heat treatment on the coarsening of ?? precipitates in rejuvenation treatment of the used gas turbine blade IN738LC worked for 60000 h. During long-term heating (simulated under the service conditions). After the sample preparation and rejuvenation treatment, long-term heating was carried out at 900 & xfffd;C and 1000 & xfffd;C for 500 to 2500 h. The SEM results showed that after rejuvenation with increasing temperature and time, ?? precipitates coarse in all the samples and the coarse ?? precipitates appear with spherical morphology. It was observed that the amount of secondary ?? precipitates decreases with the increase in temperature. When the solution treatment temperature drops, the amount of coarsened ?? precipitates has increased, which shows that the temperature rise results in a lower coarsening rate and smaller precipitate size.