Characterization of δ-phase in superalloy Allvac 718Plus^TM

Abstract

Abstract Nowadays, the trend goes to better and more efficient gas turbine engines with lower emissions, greater durability and lower cycle costs. To this end, new materials such as Allvac 718Plus TM , should enhance the high temperature performance. The appearance, morphology and control of the δ-phase are of special interest because of their critical influence on grain structure, grain size and mechanical properties. In this work, the evolution and the morphology of the δ-phase during heat treatment between 900 and 1000°C for annealing times of up to 8 h are investigated in order to determine the time – temperature – precipitation diagram and to understand the phase morphology. For this, different analysis methods are applied, such as light microscopy analysis with computer-aided quantitative metallography, dual beam focused ion beam and both scanning electron and transmission electron microscopy.