Ab-initio approach to study hydrogen diffusion in 9Cr steels

V.P. RAMUNNI; C. HURTADO-NOREÑA; P. BRUZZONI

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011

0921-4526

We calculate the equilibrium energies and migration barriers of Fe, Cr and H interstitial defects in α-FeX(X =Cr). We use the ab-initio electronic structure code, SIESTA, coupled to the Monomer method to find activatedstates (or migration barriers), in order to study atomic defects diffusion. Ab-initio calculations reveal that in the presence of Cr the H migration barriers are higher than in pure BCC Fe. On the other hand, our permeation tests on 9Cr-91Fe alloys reveal a permeation coefficient 10 times lower and a diffusion coefficient 200times lower thanin pure, annealed iron. Focusing on our experimental results, we explore very simple model of new H trapping sites and possible migration paths that can explain the experimental observations.