In general, hydrogen enters steels through various methods, including heat treatment, electro-plating, fabrication as well as through surrounding environment. Subsequently, the introduced hydrogen diffuses through the microstructure of the material and interact with the existent defects affecting the mechanical properties in many ways. Despite many efforts, hydrogen embrittlement (HE) still poses an acute risk on metals in general and on high-strength steels in particular leading to severe degradation in their mechanical behavior. Unfortunately, a complete understanding of hydrogen behavior and embrittlement is still lacking.

On the other hand, stainless steel in nuclear reactors is subjected to a combination of sever conditions. Internal stresses from swelling of the fuel, corrosion from interaction with cooling water, and irradiation. Additionally, a significant proportion of the radiation-produced crystal lattice-defects are responsible for the changes in mechanical properties in steels. During operation a reactor vessel is exposed to avalanche of neutron irradiation fluxes, that impacts the mechanical properties of the stainless steel causing degradation. This consequently triggers the change in the critical temperature of ductile to brittle fracture transition and other characteristics of the fracture viscosity of steel. Plenty of different studies have been carried out to assess the effect of these reactor conditions explicitly. However, the effect of a combination of any of these effects together is still an immature field of research. Both corrosion and irradiation are time dependent and accumulating long term process. Carrying out experimental or atomistic level simulations to study the effect of these two processes simultaneously can be difficult if not impossible. In this abstract we investigate the effect of irradiation on hydrogen embrittlement due to corrosion using cluster dynamics simulation. Nucleation and growth of nonstoichiometric vacancy and intersitial clusters that are a combination of Fe~i~, V~Fe~, and H are investigated over experimental time scales. 

In the current study, the effect of irradiation dose and temperature on the concentration of nonstoichiometric clusters of different sizes will be determined. Moreover, the results compare between different examples of no hydrogen exists and/or no radiation, where the different concentrations of vacancy clusters of different composition are plotted on a color map.  In addition, the concentration of hydrogen in stainless steel will be dictated by the rate of corrosion at the given temperature. Using these results, we can predict and asses the characteristics of hydrogen embrittlement in stainless steel due to corrosion and irradiation.

 

References:

\[1\] “Off-stoichiometric defect clustering in irradiated oxides”, S. Khalil, T. Allen, A. El-azab, Chemical Physics, Vol. 487, 2017, Pages 1-10

 


Hydrogen Embrittlement Characteristics in Irradiated Stainless Steel

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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