Abstract
Polycrystalline nickel-based superalloys tend to have large grains within component areas where high loads are dominant during operation. Due to these large grains, caused by the manufacturing and cooling process, the orientation of each grain becomes highly important, since it influences the elastic and plastic behaviour of the material. With the usage of the open source codes NEPER and FEPX, polycrystalline models of Inconel 738 LC were generated and their elastic and crystal plasticity behaviour simulated in dependence of different orientation distributions under uniaxial loading. Orientation distributions close to the [100] direction showed the lowest Young’s moduli as well as the highest elastic strains before yielding, as expected. Orientations close to the [5¯89] direction, showed the lowest elastic strains and therefore first plastic deformation under strain loading due to the highest shear stress in the slip systems caused by the interaction of Young’s modulus and the Schmid factor.
Highlights
Stationary gas turbines, as used in gas power plants, can be started from cold to a maximum output in less than 30 min [1]
Nickel-based superalloys show a high elastic anisotropy factors up to 2.7 [5]; the local orientation distribution of the grains within the gauge section have a significant influence on the elastic response of the component
It could be shown that grain orientations close to the [100] direction provide lowest Young’s moduli and highest elastic strains before yielding
Summary
Stationary gas turbines, as used in gas power plants, can be started from cold to a maximum output in less than 30 min [1]. Current design paradigms are based on deterministic lifetime approaches, which lead to conservative designs and inefficient component geometries caused by high safety factors In recent years, these deterministic approaches were successfully replaced by probabilistic approaches, which are based on the statistical distribution of factors, which affects the high temperature fatigue life of the considered materials [2,3,4]. Nickel-based superalloys show a high elastic anisotropy factors up to 2.7 [5]; the local orientation distribution of the grains within the gauge section have a significant influence on the elastic response of the component. This leads, in combination with the low amount of grains, to a non-averaging of mechanical properties as known for isotropic materials. Some austenitic steels show higher elastic anisotropies [6,7], but due to significantly smaller grains known for stainless steels, mechanical properties are averaging over the high amount of grains, and the macroscopic material behaviour can be classified as isotropic
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