These can be taken online or offline in a matter of minutes to produce power, a suitable balancer to the green energy sources. The rapid changes in energy production set high reliability on the gas turbines components. These changes introduce a cyclic exposure of the components which leads to thermomechanical fatigue load conditions.
At peak loading the components will be subjected to high temperature in combination with high mechanical load, hence exposed to creep/stress relaxation.
The increased usage of gas turbines on the energy market sets high demands on the environmental impact and efficiency, meaning that better prediction methods and more realistic behaviour of the materials are needed in the simulations during the design phase.
Single-crystal nickel-base superalloys
The major class of materials used for the first stage turbine blades is single-crystal nickel-base superalloys, due to their excellent high temperature properties. See Fig. 1 for a typical microstructure image of a single-crystal superalloy. These blades are manufactured through investment casting, a perfectly aligned specimen is never achieved during this process, hence misalignments in crystal orientation need to be accounted for, see Fig. 2.
However, the anomalous elastic and inelastic material behaviour of single-crystal nickel-base superalloys makes the evaluation/design process rather complex, see Fig. 3. Hence, insufficient knowledge of the material behaviour often leads to the use of large safety factors that leads to conservative designs, which in turn render loss in performance and efficiency.