The Ni-base superalloy GTD-111 is widely used in manufacturing of the first stage blades of high power land-based gas turbines. In spite of its important role in increasing the performance of gas turbines, due to high temperature capability, there are little data on the microstructure, deformation mechanisms and mechanical properties of the alloy. The aim of present paper is to determine in details these properties. Microstructural characteristics of the alloy were assessed by means of optical, scanning and transmission electron microscopy. The tensile behaviour of GTD-111 has been studied in the temperature range 25–900 °C. The results showed abnormal variations in tensile properties with increasing temperature. TEM observations confirmed that these behaviours were affected by the properties and a change in the mechanism of deformation of GTD-111 at high temperatures. From creep test results, Larson–Miller and Monkman–Grant plots were produced which are used for life prediction. It was also observed that several creep deformation mechanisms operate at various combinations of temperature and stress.

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