Abstract The Ni – base superalloys, which combine unique physical and mechanical properties, are used in aircraft industry for production of aero engine most stressed parts, as are turbine blades. From this reason a dendrite arm spacing, carbides size and distribution, morphology, number and value of ?? - phase are very important structural characteristics for blade lifetime prediction as well as aero engine its self. In this article methods of quantitative metallography (software LUCIA for carbides evaluation, measuring of secondary dendrite arm spacing and coherent testing grid for ?? - phase evaluation) are used for evaluation of structural characteristics mentioned above on experimental material – Ni base superalloy ŽS6K. The high temperature effect represented here by heat treatment at 800°C followed with holding time about 10 hours, and cooling rate, here represented by three various cooling mediums as water, air, and oil, on structural characteristics and application of quantitative methods evaluation are presented in this paper.