Hydrogen Interaction with Residual Stresses in Steel Studied by Synchrotron X Ray Diffraction

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.</jats:p

Thermal stability of retained austenite in low alloyed TRIP steel determined by high energy synchrotron radiation

TRIP-steels offer a good combination between strength and ductility. Therefore TRIP-steels are widely used in the automobile industries. The aim of this work is to study the stability of involved phases during heating and to identify the kinetics of the occuring phase transformations. For that purpose, in-situ diffraction measurements, using high energy synchrotron radiation were conducted. The analysis revealed the decomposition of the metastable austenitic phase into carbide and ferrite along the heating process and the regeneration of the austenite by further heating of the sample.</jats:p

The Influence of Hydrogen on Thermal Desorption Processes in Structural Materials

AbstractHydrogen embrittlement is a form of environmentally assisted failure caused by the action of hydrogen, often in combination with residual or applied stress that results in a reduction in the load-bearing capacity of a component. It was found that hydrogen has a direct influence on the lattice parameter and on the thermal expansion characteristic. Hydrogen's desorption behavior in this process and its effects on the mechanical behavior of those materials are discussed in detail