Abstract
Two different material batches made of random and textured orientated polycrystalline nickel-base superalloy René80 were investigated under isothermal low cycle fatigue tests at 850 °C for a notched specimen geometry. In contrast to a smooth specimen geometry, no significant improvement in fatigue behaviour of the notched specimen could be observed for the textured material. Finite element simulations reveal an area along the notch where high stiffness evolves for the textured material, which lead to nearly similar shear stresses in the slip systems compared to a random orientation distribution and therefore to no distinct differences in the lifetime.
Highlights
The worldwide demand for the reduction of CO2 emissions during power generation and the associated increased usage of renewable energy sources has lead to fluctuation in the power supply and can cause problems with regard to power grid stability
The stress amplitude σa,notch decreases with a decrease of total strain amplitude, which results in longer lifetimes
The influence of a random and textured grain orientation distribution on the mechanical as well as fatigue behaviour was investigated for the polycrystalline nickel-base superalloy René80
Summary
The worldwide demand for the reduction of CO2 emissions during power generation and the associated increased usage of renewable energy sources has lead to fluctuation in the power supply and can cause problems with regard to power grid stability. In order to fill in these gaps, gas power plants are used due to their ability to generate power in short times. Stops and load changes from part to full load, the materials in the hot gas section and especially the turbine blades have to withstand significantly fluctuating mechanical and thermal loads. Thermo–mechanical fatigue, high-temperature fatigue behavior and creep effects of the turbine material must be investigated in order to reach high efficiencies with simultaneous economic design aspects. Since component testing is very complex and expensive, generally, a standardized specimen of the used material is examined under high-temperature fatigue conditions. Numerical models are indispensable during the design process in order to predict the deformation and fatigue behavior under various load and temperature conditions. Based on experimental observed and measured mechanical material responses, models such as the commonly used Ramberg–Osgood or the Chaboche model are used to describe the nonlinear stress strain relationship for materials under high-temperature conditions [2,3,4]
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