Nowadays, the trend goes to better and more efficient gas turbine engines with low emission, great durability and low cycle cost. Therefore, a new grade, Allvac 718 Plus™, shall enhance the high temperature properties. The appearance, morphology and control of δ-phase are of special interest because of their critical influence on grain structure, grain size and mechanical properties. In this work, the evolution of the δ-phase during a heat treatment between 900 and 1000°C for annealing times of up to 8 hours is investigated in order to determine the time temperature precipitation (TTP) diagram and to understand the phase morphology. For this, different analysis methods are applied, such as light microscopy analysis with computer-aided quantitative metallography, differential scanning calorimetry (DSC) and both scanning electron (SEM) and transmission electron microscopy (TEM).