With the increasing use of renewable energy, power plants with gas turbines often operate under varying loads. Changes in load and temperature during operation have a high impact on the lifetime of turbine blades. A better understanding of operational stresses and the lifetime of the material can help improve design and durability. In order to simulate the behavior of turbine blades during operation, we are investigating isothermal low cycle fatigue (LCF) tests with the Ni based alloy René80. The aim is to produce a statistical correlation between grain orientation, microstructural fatigue processes and the lifetime of the material.