Comprehensive Microstructural Evaluation of Precipitation in Inconel 718

Abstract

Recent advances in industries require materials with greater strength at higher temperatures without failure in service. Inconel 718 is a precipitation strengthened Nickel–iron-based superalloy for application at high temperatures. In view of this, the present study is aimed at monitoring the degradation during service due to microstructural changes. Inconel 718 alloy is solution annealed at 980 °C for 1 h, then subjected to aging treatment at different temperatures 650, 750, 800, 900 °C for times up to 100 h. On solution treatment, there was a decline in strength, but after aging process, there is an enhancement of strength. The heat treatments and respective microstructural phases, which in turn influence both ultrasonic velocities and elastic properties, have been studied. Further, by ultrasonic measurements the precipitation behavior in Inconel 718 can be monitored in nondestructive manner.