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- Energy dispersive diffraction (2) (entfernen)
Energy dispersive synchrotron diffraction for in-situ analyses of hydrogen behavior in steels
(2013)
The extent of hydrogen embrittlement phenomenon is dependent on the interaction of hydrogen with the material i.e. diffusion behavior, lattice distortions, phase transformations and residual stresses developments. For the better understanding of the hydrogen interaction with the metal, possibilities of performing in-situ observations of the mentioned factors has to be accomplished. The EDDI (Energy Dispersive Diffraction) beamline at the BESSY II facility in Berlin provides this possibility and was used in order to investigate the aspects of this phenomenon in in-situ scale.
The energy dispersive method entails a synchrotron X-ray white beam with a wide energy range (20–120 keV) which allows a fixed position of the sample and the detector, and combined with the high photons flux it allows a very short measurement time for obtaining a full scale X-Ray Diffraction patterns.
In this contribution, the successful usage of high energy X-rays, applied for the first time for hydrogen behavior observations, provided the ability for evaluating in-situ the hydrogen diffusion behavior and the hydrogen interaction with stresses fields in the material.
Steel samples were charged with hydrogen and examined by Synchrotron radiation.
Two different methods were used in this research; the first is diffusible hydrogen concentration evaluation extracted from the lattice distortions, i.e. changes of the lattice parameter. The second is calculation of the residual stresses present in the sample and the interaction of hydrogen with them, using the known sin2ψ method.
Hydrogen interaction with residual stresses in steel studied by synchrotron X-ray diffraction
(2014)
The residual stress state in a material has an important role in the mechanism of cracking, induced or assisted by hydrogen. In this contribution, the beamline EDDI in BESSY II instrument in Berlin was used in order to investigate the influence of hydrogen upon the residual stresses state existing in a Supermartensitic stainless steel sample. The method used for investigating the residual stresses is the sinus square ψ method. This method involves the usage of high energy X-ray diffraction in order to measure the residual stress state and magnitude. It was found that hydrogen presence has a significant influence upon the magnitude of the residual stresses, as its value decreases with high hydrogen content. This effect is reversible, as hydrogen desorbs from the sample the residual stress magnitude gains its initial value before hydrogen charging.